Yes, you can. Cook the burgers according to the recipe. Leave them to cool to room temperature then place on a baking sheet and place in the freezer for an hour. Once almost frozen place in layers in a freezer bag or airtight container place wax paper between the burgers to prevent them from sticking together. Thaw the burgers in the fridge overnight then cook from frozen on the hob or in the oven until they are piping hot.