Yes, they can. It's best to freeze them as soon as possible after baking. Alternatively, mince pies can be frozen before they are cooked. In this instance, freeze them in the baking tin then, once frozen solid, remove them from the tin and keep them in a freezer bag for up to 3 months. When ready to bake, put them back into the baking tin and cook from frozen until puffed and golden. Don't forget to brush with beaten egg before sliding them into the oven.