Unfortunately, I don't advise freezing the paneer sandwiches for this dish as the cornstarch coating will become dense and chewy. That said, you can make some headway on your preparations. You can either: - make both the onion paste and tomato-cashew paste and freeze them, or - make the gravy and freeze it. Just don’t add dry fenugreek leaves, garam masala and cream. On the day of cooking, heat the gravy in a pan. If necessary, feel free to add bit of water. Allow it to come to a gentle simmer, then add dry fenugreek leaves, garam masala and cream.