For Ruby Tandoh, history has been written in biscuit crumbs, birthday cakes and bubblegum. Here, she takes us through her life on a plate... 

At 16, I wanted to be a meteorologist. So with the same dedication I later applied to baking, I set to learning everything I could about the heavens. It wasn’t long before I could read the clouds – wispy cirrus, pregnant nimbus – and in my own amateurish way, predict whether the day would be not just bright or overcast, but also good or miserable. I became a master of pathetic fallacy, foreseeing storms and break-ups with little more than an upwards glance.

When I left home for university in London, my soothsaying was swiftly thwarted. The city broke the sky into illegible snippets, woolly clouds flashing into view one moment only to dip behind a building the next. Even the stars were usurped by the winking towers of Canary Wharf. I climbed Hampstead Heath one day for a better view of the sky but found it less lucid than ever.

Forced to look elsewhere for signs, food became my new prophet. A breakfast of weak coffee and biscuits wasn’t just a bad start to the day – it was an inauspicious sign. A good ice cream could be the silver lining to a downbeat month. Once, a disappointing doughnut moved me to tears. I predicted the day's calibre based on the contents of my cupboards, and a plate licked clean became the surest barometer of my mood. I didn’t take these forecasts too seriously, but I did relish the order they wrought from the confusion of my new London life.

There was one meal, in a station cafe on the way to visit my granddad, which stood out as particularly prescient. I ordered a pasty and sat at a window table with a view of the taxi rank. It arrived flabby, microwaved and grey, presented on a neatly folded paper napkin on a paper plate, plastic knife and fork laid carefully to rest either side. I picked at the dismal spread for five minutes then surrendered and just watched the grease and gravy inch across the napkin. My granddad, too ill to recognise me when I arrived at his hospital bedside, died later that week.

My life has been mapped in food for as long as I can remember. A childhood trip to Legoland stayed in my memory, not for the thrill of the fair, but for the taste of cinnamon-dredged doughnuts. One family holiday to Scotland would have faded to obscurity if not for the lingering sweetness of a stack of pancakes we had in a cafe in the Highlands. I can chart my progress through normal milestones – birthdays, new schools, starting my period – but it’s only through food that these episodes draw into focus. For eight years now, I haven’t been able to eat chicken and mash without reliving the nausea of my first kiss. He tasted of Strongbow and cigarettes and, as soon as I arrived back home, Mum set down the chicken dinner she’d saved for me. I could barely eat it for the visions of the boy’s windmilling tongue.

My parents still have an illustrated cookbook that has ‘birrts’ scrawled across every one of the 100 or so pudding recipes, courtesy of my three-year-old self as I planned for my fourth ‘birrts’. My growing hunger that bled into my taste in literature: everything from recipe cards to The Very Hungry Caterpillar were pored over, biscuit crumbs lodged deep in book spines. Among volumes about love, war, life and death, I looked for something to sate my appetite.

My tastes became even sweeter as I grew, though I remained far from sugar and spice myself. I wouldn’t let my hair be brushed, nor my T-shirts ironed, I wore boys’ shorts to school and cherished a pair of snakeskin-print Dr. Martens boots, which, though sartorially questionable, were perfect for kicking. It was a time of cheese on toast and bubblegum – so much bubblegum that I had to stall the moving of my bunk bed to a new room in order to buy time to frantically chip away the hundreds of dried-out gobs stuck to the back of my headboard.

By the time that I reached secondary school I was all angles: flipper feet, knock knees and broad shoulders that finished in big bony nubs – still do – as if to warn to anyone who might want to rest their head there. I ate as I pleased and remained rangy in spite of my doggedly optimistic purchasing of 32A bras.

Oddly for teenagers at an all-girls grammar school, my friends and I were happily immune to body neuroses. We ate chips for lunch, had canteen feasts on birthdays and spent our spare coins, chiming impatiently in our blazer pockets all day, on sweets as soon as we left the school gates. I must have sensed that this age of innocence wouldn’t last for ever, though, because by Year 10, I was eating with the gusto of someone who suspects that each meal might be their last. As it happened, the end did lie just around the corner: across a pock-marked rugby pitch and down a gravel drive to the doors of the boys’ school.

I promised that I would make my boyfriend, who we shall call X, dinner. By the time he arrived, I’d scrawled a list on the back of a piece of coursework, shopped for ingredients, cleared a square of the communal student kitchen for myself and made lentil dal. He waited in my room while I draped pastry over a dish of apple pie filling and scrubbed the sharp smell of garlic from my fingers. Later, keeping my eyes fixed on X and away from the accusing presence of The Female Eunuch, sitting unread on my bookshelf, I brought X hot chocolate and fell into bed beside him. I ignored the growls of my stomach. A familiar acid burn throbbed in my chest, which I told myself – as X softly kissed the crown of my head – could be love.

Somewhere between my first boyfriend (who stared freely at my bottom despite never having even held my hand) and my first love, X, my relationship with food had soured. I saw the inside of the toilet so much during those few years that even now I can remember the soft curves of the ceramics, the hiss of the cistern and the bowl flushed clean. If I’d been well enough to make my usual forecasts, I would’ve found them more accurate than ever: like clockwork, I ate my panic and retched away the shame. All the while, I channelled my urge to cook in other directions, feeding those I loved until they were as fat as pheasants.

I even went into modelling for a while, as if to give my illness some justifying purpose. I dashed between castings with masochistic zeal, squeezing myself into sample clothes many sizes too small. I crunched only numbers during this time – calories, pounds and inches – but of course the sums never did add up. There’s a moment of horrified realisation in Bridget Jones’s Diary when Bridget realises that knowing, off the top of one’s head, the calorific content of hundreds of foods isn’t a sane way to live. My own epiphany came when I calculated that the number of minutes I’d spent counting calories that day was greater than the number of calories eaten. I stopped returning my agency’s calls and enjoyed a valedictory ice cream, though not without making a mental note to run off those 15 grams of fat later at the gym.

In spite of my best efforts, I fell steadily under food’s spell once more. I read recipe books and found a job in a cake shop. On slow weekends, I would set out to the farmers’ market with my scarf clutched tight to see the carrots like arthritic old fingers, potatoes with winking eyes. As X and I drifted apart, I discovered pockets of time that I’d rarely known before: mist-drenched mornings and slow evenings when I read restaurant reviews and went to sleep dreaming of carpaccio, soufflé and squid.

I learned about ingredients, techniques and flavours until I had a dozen notebooks of ideas, recipes and shopping lists. Diary entries were cut off mid-sentence with ‘blackcurrant and bay?’ or ‘rosemary pecan pie!’ in thick black pen. I spent more time in the kitchen and less time with my head down the toilet. I mustered up the courage to go travelling, where I found a job in a hostel kitchen in Lisbon and spent three of the best months of my life hauling shopping bags up and down the steep, cobbled streets, and nursing puff pastry in the 35°C heat.

When I returned home from Portugal that autumn, I made the dish that was to put my fraught food history definitively to rest – a batch of glazed ring doughnuts made with sweet potato and autumnal spices. There was no eureka moment, though. At first, the doughnuts were flat, then solid, then too sweet or too bland: I baked a dozen batches of them over the course of a week, tweaking each time with a pinch of cinnamon here, a dash less milk there or a couple of sunny yolks stirred into the mix.

I never did manage to quite perfect the recipe, but by the time the audition for The Great British Bake Off rolled around, I'd run out of yeast and willpower, so I just packed six of the least misshapen ones into an old takeaway tub and set out to the venue. Those bulbous doughnuts marked the beginning of my newest adventure in food, and we started filming a few months later. Food that had the last laugh: it was only when I surrendered to it that I learnt to enjoy it on my own terms. The better I got to know it, the less fearful I became. I was healthier – and hungrier – than ever.

If I had any worries that baking would just be a phase – like gymnastics aged nine, or banjo (forgive me) when I was 17 – those fears were quickly laid to rest. Each week that I survived Bake Off, my repertoire expanded; for every Guardian baking column I wrote, I wanted to pen two more. And by the time it came to my book, Crumb, I had so many flavours that I wanted to combine, and ideas to explore, that I barely had room to fit them all between the book’s two covers. Over five fraught months, between January and June of this year, I wrote Crumb and painstakingly teased these nebulous thoughts and fancies into something concrete. When I first received a copy of the finished book all I could do was to slowly tip it from one hand to the other, reassured by its weight in my palms – this was no mirage.

Food has finally fallen into step with my lilting rhythms. Mornings now crawl into action through thick porridge and coffee and, as the day picks up pace, so does my appetite. I pick, snack and nibble as the fancy takes hold, eating blood-orange sorbet in January or furtively unrolling my McDonald’s paper bag on the bus and slipping chips, one by one, through salt-stung lips. I still succumb to food’s charms too enthusiastically at times, though. For my last birthday, I spent so long baking cakes, brioche buns and biscuits in honour of the big day that, by the time I’d finished cooking, I was no longer sure whether the food celebrated the occasion or the celebration was in aid of the food. Either way, nobody at the party went hungry.

Lunchtimes in the city are particularly nourishing for me. It’s a feast of people-watching: men in suits licking their fingers clean, guilty eaters with a pain au chocolat in one hand and a compensatory pot of edamame beans in the other. Some people eat as they stride back to the office while some barely make time for a smoke. My favourites find an unoccupied bench and, with a conspicuous lack of haste, unclip a lunchbox, survey its contents and tuck in. I like to think that they’re doing as I still do from time to time, reading their packed lunch like a set of tarot cards – olives mean good luck, tuna means bad – and forming their own food forecast for the day. I suspect that we’re the happiest of the lot.

Crumb: The Baking Book by Ruby Tandoh (Chatto & Windus) is out now.