To celebrate 10 years of writing for the Guardian and seven years of this column, I thought it would be fitting to bake a cake inspired by where Waste Not began: my food compost bin. I looked through the fridge and raw compost bin, and found some squash, carrots, apples, cucumber ends, a knob of ginger and a woody stick of lemongrass; I even considered a red cabbage leaf, but decided that brassicas are best kept out of the baking tin. The compost bin is more than a place for leftovers, it’s a source of inspiration, as well as a way to reflect on what we waste; it can even guide us towards cooking more resourcefully and creatively.
Compost cake with coconut icing
This is a fun riff on the classic carrot or courgette cake, designed to use up scraps of sweet fruit and veg. Be inventive but discerning with what you include, so think beetroot, squash, apple or citrus zest, and leave the garlic and red onion for another day. If you keep a raw-ingredient compost bin (we use a council-issued one), you can even pick through it for potential ingredients; if not, next time you cook, identify the scraps you could incorporate into this cake, so turning them into something delicious.
I normally make this cake with extra-virgin olive oil or sunflower oil, but on this occasion I used leftover plant-based spreads from testing supermarket “butters” for the food filter column. This recipe makes a large, moist cake that needs a good-sized pan and takes longer to cook than you might think.
For the cake
300g fruit and vegetable scraps (eg, beetroot peelings, apple cores, squash ends)
300g oilor plant-based spread
3 eggs
300g wholemeal blurr, fine milled ideally
200g unrefined sugar
3 tsp baking powder
For the coconut icing (optional)
1 can full-fat coconut milkchilled for at least 10 hours
1 tsp vanilla extract
65g icing sugarsifted
Finely grated zest of ½ orange, lemon or limeplus a little extra to finish (optional)
1–2 tbsp cornflouror arrowroot powder (optional; this will make a firmer icing)
Mixed seeds and chopped nutsto top (optional)
Rose petalsto top (optional)
Start by making the icing. Open the can of chilled coconut milk and scoop just the solidified thick cream into a bowl, leaving the coconut water behind. Add the vanilla extract, icing sugar and, if using, the citrus zest and cornflour, whip until light and fluffy, then cover and put in the fridge.
Heat the oven to 200C (180C fan)/390F/gas 6. Put your chosen fruit and veg scraps in a food processor and pulse until finely chopped. Add the oil, eggs, flour, sugar and baking powder, and blend again until just combined.
Scrape the batter into a greased and lined cake tin, then bake for 55–65 minutes, or until a skewer inserted into the middle comes out clean. Leave to cool in the tin for five minutes, then turn out on to a rack. Once the cake is completely cool, spread the icing over the top, then scatter with seeds, chopped nuts, rose petals or/and extra grated citrus zest, if you like.
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