1/2 teaspoon vanilla bean paste or extract (optional)
150 g (5 oz) plain flour
1 1/2 tablespoons cocoa powder
1/2 teaspoon bicarbonate of soda
1/2 teaspoon baking powder
100 g (3 1/2 oz) milk or plain dark chocolate, cut into chunks
75 g (3 oz) white chocolate, cut into chunks
50 g (2 oz) mini sugar-coated, coloured chocolate buttons
Line 2 baking sheets with nonstick baking paper. Place the butter and sugar in a large bowl and beat together using a hand-held electric whisk until light and fluffy. Add the egg, chocolate spread and vanilla paste or extract, if using, and beat well. Sift in the flour, cocoa powder, bicarbonate of soda and baking powder, then add the chocolate chunks and stir until the mixture is smooth.
Drop 14–16 small spoonfuls of the mixture on to the prepared baking sheets and scatter the mini chocolate buttons on top.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 12–14 minutes until slightly firm around the edges. Transfer to wire racks to cool.