- 100g/3½oz unsalted butter
- 250g/9oz caster or brown sugar
- 50ml/2fl oz sunflower oil
- 25g/1oz arrowroot, cornflour or cocoa
- 2 tsp vanilla extract
- 4 medium free-range eggs
- 80ml/2½fl oz milk
- 100ml/3½fl oz double cream
- 300g/10½oz plain flour
- 3 tsp baking powder
- Line the base of a deep 20cm/9in square cake tin with non-stick paper and preheat the oven to180C/350F/Gas 4.
- Melt the butter over a low heat in a small pan, pour it into a bowl with the sugar, oil, cornflour (or arrowroot or cocoa) and vanilla. Beat well until smooth, then whisk in the eggs followed by the milk and cream.
- Sift and beat the flour and baking powder into the butter mixture in batches until smooth, then spoon into the prepared tin and bake for 50-60 minutes (for a large cake). Keep a careful eye toward the end of the cooking time, and cover with foil if the cake is getting too dark. For cupcakes, fill the papers about three-quarters full then bake for about 20-25 minutes.