For the cake
For the frosting
Heat oven to 160C/140C fan/gas 3. Grease two 20cm sandwich tins with a little dairy-free sunflower spread, then line the bases with baking parchment.
Put 1 large avocado and 300g light muscovado sugar in a food processor and whizz until smooth.
Add 350g gluten-free plain flour, 50g cocoa powder, 1 tsp bicarbonate of soda, 2 tsp gluten-free baking powder, 400ml unsweetened soya milk, 150ml vegetable oil and 2 tsp vanilla extract to the bowl with ½ tsp fine salt and process again to a velvety, liquid batter.
Divide between the tins and bake for 25 mins or until fully risen and a skewer inserted into the middle of the cakes comes out clean.
Cool in the tins for 5 mins, then turn the cakes onto a rack to cool completely.
While you wait, start preparing the frosting. Beat together 85g ripe avocado flesh and 85g dairy-free sunflower spread with electric beaters until creamy and smooth. Pass through a sieve and set aside.
Melt 300g dairy-free chocolate, either over a bowl of water or in the microwave, then let it cool for a few mins.
Sift 25g cocoa powder into a large bowl. Bring 125ml unsweetened soya milk to a simmer, then gradually beat into the cocoa until smooth. Cool for a few mins.
Tip in the avocado mix, 200g sifted icing sugar, melted chocolate and 1 tsp vanilla, and keep mixing to make a shiny, thick frosting. Use this to sandwich and top the cake.
Cover with sprinkles or your own decoration, then leave to set for 10 mins before slicing. Can be made 2 days ahead.