I make quesa all the time. The whole family loves it on Sunday when we barbecue. I use:
1 large block of Velvetta
1 can rotell tomatoes (I use original recipe) Hot is very hot
1 can cream of celery soup
Cut the cheese into chunks, cover with rotell and soup in a microwave safe bowl. Microwave at 1min. intervals and stir until completely melted. Be sure not to overcook as the cheese will scorsh.
A friend told me she uses the soup as it makes the cheese dip creamier and it doenst gel up...I though ick celery soup .....but it does work and makes the sauce just like the restaurants serve. Serve with nacho chips