Chocolate custard muffins

Roger Pizey has been Marco Pierre White's pastry chef since way back at Harvey's in 1987, and is undoubtedly one of our finest. His book Small Cakes (Jacqui Small, £8.99) is out this month and we've got a competition to win a signed copy. To enter, email a pic of your best small cake to guardian@danlepard.com before May 5. To start you off, here's my recipe for the best chocolate muffin you'll ever eat.
50g cornflour
3 level tbsp cocoa
100g dark soft brown sugar
225ml cold water
75g unsalted butter, cubed
125g dark chocolate, broken small
75ml sunflower oil
2 tsp vanilla extract
2 large eggs
125g caster sugar
125g plain flour
2½ tsp baking powder

First make the custard: put the cornflour, cocoa, brown sugar and water into a saucepan and whisk together over a medium heat until boiling, very thick and smooth. Remove from the heat, beat in the butter and chocolate until melted and absorbed, then add the oil, vanilla and one of the eggs, and beat again until combined. Add the remaining egg and the caster sugar, and beat again until smooth and thick.

Measure the flour and baking powder into a bowl, stir together, then sift directly on to the custard and beat through until combined. Spoon into a dozen paper muffin cases sitting in the pockets of a muffin tray; heat the oven to 180C/350F/gas mark 4 and bake for 25 minutes.