You can make Palak gravy and freeze it. Do not add paneer cubes /veggies in it. Whenever required, thaw and reheat it and add fresh paneer/tofu/vegetables. Add a tbsp of fresh cream/butter before serving(if you don't have any dairy/dietary restrictions). You can also blanch Spinach, puree it and then freeze. Thaw the puree and use to make Gravy anytime you need. Freeze the puree/spinach gravy in small portions which are easy to thaw. Do not freeze again reheated Palak gravy