if you directly buy the marinated / cooked ones from T&T or other Chinese supermarket, it's a lot easier to prepare. I often found the packed marinated ones from T&T's horizontal display fridge ( not freezer) in their cooked food area. Usually there's 5 days from the "packed on" date to the Best Before date. But you can easily freeze them for a much longer time at home if you bought extra amount of them. Before eating them, I suggest you to rinse them, and then steam them in a pressure cooker for 30 ~ 50 minutes ( cut them into smaller pieces before steam them, if necessary). Then, they are ready to serve. If you like, you can also add one more step: put them in a nonstick pan with a little bit cooking oil, after the steaming process. Heat them slowly until the fat spots are melt off and the meat skin shows sticky gelatin. Before steaming or heating in a pan, you can also add some seasonings as you like for better or different flavors. But they taste good even without additional seasonings.