What follows is the 1981 unmodified recipe from Bisquick. My photo is missing the tomatoes on top because I didn't have any, not because it's not good that way! You can, of course, make the recipe lower fat by using skim milk, one of the skinnier forms of Bisquick available today, and low fat cheese. If ground beef isn't your thing, just substitute some other type of meat or protein and change the name to "Impossible Ham and Cheese Pie" or "Impossible Tofuburger Pie" or whatever works for you!
Impossible Cheeseburger Pie
1 pound ground beef
1 1/2 cups chopped onion
1/2 tsp salt
1/4 tsp pepper
1 1/2 cups milk
3/4 cup Bisquick baking mix
2 tomatoes, sliced
1 cup shredded cheddar cheese
Heat oven to 400 degrees. Grease a 10" x 1.5" pie plate.
Brown beef and onion; drain. Stir in salt and pepper. Spread in pie plate.
Beat milk, Bisquick, and eggs until smooth. Pour into pie plate.
Bake 25 minutes.
Top with tomatoes and sprinkle with cheese.
Bake until knife inserted in center comes out clean, 5 to 8 minutes.
Cool 5 minutes.
Makes 6 to 8 servings.