Grease a large baking sheet.
Put the flour, bicarbonate of soda, cocoa powder and sugars in a bowl. Beat the egg with the vegetable oil and milk and add to the dry ingredients. Beat together to form a thick paste, adding a little more milk if the mixture feels crumbly.
Take teaspoonfuls of the mixture and roll into balls, about the size of a cherry, using floured hands. Space well apart on the baking sheet and flatten slightly.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 12 minutes until the mixture has spread and is pale golden. Transfer to a wire rack to cool.
Make the frosting by beating together the cream cheese, icing sugar, orange rind and extract, if using. Use to sandwich the cakes together. Melt the chocolate (see