150 g (5 oz) soft butter or margarine, plus extra for greasing
250 g (8 oz) caster sugar
finely grated rind of 1 orange or 1 teaspoon orange essence
250 g (8 oz) plain flour
pinch of salt
1/2 teaspoon bicarbonate of soda
150 g (5 oz) white chocolate, cut into chunks
Preheat the oven to 180°C (350°F), Gas Mark 4, and lightly grease 2 nonstick baking sheets. Beat the softened butter and sugar together until pale and creamy, then beat in the orange rind or essence and the egg. Sift the flour, salt and bicarbonate of soda into the bowl, and mix to combine. Stir in the chocolate chunks.
Arrange 6 large spoonfuls of dough on each of the 2 prepared baking sheets, leaving plenty of room for the dough to spread. Cook in the preheated oven for 10–12 minutes, until lightly golden.
Transfer to wire racks to harden and cool slightly. Serve warm or cold. Any leftover cookies can be stored in an airtight tin for 2–3 days.