Preheat the oven to 375F. Bring the stock or water to the boil in a large lidded casserole dish. Add the meat and masala paste and simmer, stirring occasionally. Cover and put in the oven, and cook for 20 minutes. Inspect it and add water if needed. Cook for another 20 minutes and test the meat for tenderness: it should still "resist" a little and feel not quite ready. If it's reached this stage, remove the casserole from the oven, remove the meat, cool it, package it in plastic containers or Ziploc bags, and freeze: or refrigerate until needed (if you're going to need it in no more than 8 hours). Reserve the stock: it too can be frozen and added to Balti sauce or curry sauce as desired.