1 (1 lb.) pkg. Velveeta mexican hot cheese
1 (1 lb.) pkg. Velveeta mexican mild cheese
1 (15 oz.) can tomato sauce
1 (1 lb.) ground beef
1 medium onion, chopped
1 (4 oz.) can mushrooms (optional)

Brown ground beef and onion. Blend cheeses and tomato sauce in crock pot or on very low heat on stove top. Add beef and onion mixture to cheese and tomato sauce. Add mushrooms. Serve warm with nachos or taco chips.