Put the flour, bicarbonate of soda and sugar in a bowl and mix through. Add the butter and rub in with the fingertips until the mixture resembles breadcrumbs.
Beat together the egg and milk in a separate bowl. Add the chopped chocolate and glacé cherries, then mix into the flour mixture and stir well until smooth.
Drop heaped spoonfuls of the cookie mixture, well spaced apart, on to a greased baking sheet and bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 10–12 minutes until lightly golden. Leave to harden on the tray for 2 minutes, then slide off on to a wire rack or plate to cool.