In large skillet, cook beef until no longer pink. Drain.
Add taco seasoning and prepare to package directions.
Add cream cheese, cover and simmer for 5-10 minutes until cheese is melted. Stir well.
Cool meat mixture for 1 hour.
Fill each shell with about 3 Tablespoons of meat mixture.
Grease (2) 9 inch square baking dishes, and place 12 shells in each dish.
Mix salsa and taco sauce and spoon 1/2 over shells in both dishes.
If not freezing: Cover with foil and bake at 350 for 30 minutes. Uncover, sprinkle with Cheddar cheese and tortilla chips (if using). Bake 15 min until cheese is melted. Serve with sour cream and onions.
To use frozen shells: Omit cheddar and tortilla chips before freezing. Thaw in refrigerator 24 hours Bake at 350 degrees for 40 minute Add cheese and chips and cook another 10 minute.