This is my go to recipe when I would have 50 plus people for birthday parties and made chimichangas (deep fried burritos). Everyone loved it. Now with just two in the household it makes it super easy to freeze and pull out for quick meals. Just pull a bag out in the morning and pick up go along with on the way home. Mexico night is always in the freezer.
Preheat oven to 200 degrees. Place roast (or roasts) in large roasting pan or dutch oven. Do not add salt or water. Cover with tight lid and roast for 12 hours or until roast will fall apart. you can cook roasts in a pressure cooker with 1 cup water for 35-40 minutes if you can't let it cook all day or overnight.
Remove meat from pan and reserve juices (removing fat). Let cool until easily handled. Remove any bones and fat. Shred meat and set aside.
Melt shortening in large skillet. Add onions and chilies. Saute 1 minute to soften slightly. Add green chili salsa, garlic powder, flour, salt and cumin. Cook 1-5 minutes until thickened. Add enough reserved juices to make a gravy. Add in shredded meat and cook 5 minutes until thickened.
Put about 3 cups mix into 1 quart freezer bags and leave about 1/2 inch space at top. Use within 6 months. Makes about 9 cups.