To show that your sustainable when bringing in your ingredients they should be pre-measured to the exact amount you need. Also bring them in in reusable containers. Depending on which topic out of three you get depend on what you will be cooking but I would recommend looking back and seeing what you have cooked over the last three years and see which fits best into you catagory.
Hi if you try and go for a recipe or dish that doesnt use to many pots (like stirfrys or casseroles) or too high an oven temperature that is seen to be super sustainable as you are not using alot of fule in cooking or water in wash up also try to put across that you are shopping local as you wont be travelling far to get ingriedients and to include ingriedients that are in season so they wouldnt have had to be shipped or farmed artificially using intensive lights. Hope that helps.