For a casserole version, spread 1/2 the cream mixture into the bottom of a 9x13-inch casserole dish. Tear up 1/2 the tortillas and spread over sour cream mixture. Put 1/2 the meat mixture over that. Add a layer of cheese. Add salsa if desired. Repeat the layers. Sprinkle cheese over the top and bake, uncovered, at 350 degrees for 30-35 minutes or until cheese is bubbly and melted.