Homemade biscuit mix is one of my favourite things to have on hand due to its low cost and versatility. I use it a lot for dumplings because I love the economy of making them using the same pot and burner as the main course.
Measure 9 cups flour into a big bowl. Add 1/3 cup baking powder and 1 tbs salt and mix well. Work 1 lb of shortening, margarine, or butter into the mixture with your hands. Keep in canister or ziplock bag. If you use shortening or margarine this mix can be stored at room temperature but if made with butter it is best stored in the fridge or freezer. This is very fun to make when you have combined different flours and can sense their mixed textures and fragrances while working the fat into the mix, unless you are one of those dough-in-the-food-processor types.
Mix with milk to form a stiff dough for biscuits (start with a ratio of about 1/3 cup milk to 1 cup mix) and cook at about 375 degrees til they are raised and browned, about 12 minutes depending on how you have shaped them. For dumplings, make a slightly softer dough and add a seasoning that complements your main course, like thyme or tarragon for chicken soup or grated cheese for tomato based soups. Drop into pot where main course is cooking and close lid tightly; lift lid only after dumplings are puffed up and you think they are cooked. The time varies with heat and with amount dumplings/size pot ratio; check the centre of one to make sure they are cooked through. The mix makes excellent pancakes if you mix in sugar and milk to a pouring consistency; an egg is good too and optional. If your cooking liquid is sour milk or buttermilk, add a pinch of baking soda as well to cut the acid.