Preheat oven to 180℃. Line 2 baking trays with baking paper. Cream butter and sugar together in a mixing bowl using electric beaters until light and creamy.Add the egg and beat to combine.
Add the flour and stir until a dough forms. Fold through the choc bits. Chill mixture for 20 minutes.
Roll heaped tablespoonful of mixture into balls and place onto trays, leaving room for spreading. Bake for 12-14 minutes or until lightly golden around the edges. Cool on trays for 5 minutes then transfer to a wire cooling rack to cool completely. Store in an airtight container.