Place the plain digestive biscuits in a freezer bag and tap with a rolling pin until evenly crushed. Tip on to a plate.
Place 1 scoop of ice cream on each of 4 of the chocolate-coated biscuits, shaping the ice cream so that it makes a circle the same size as the biscuit. Top with the remaining chocolate-coated biscuits and sandwich together.
Roll the ice cream in the crushed biscuits until coated. Serve immediately or place on a baking sheet, cover and freeze until required.