I love that cheese sauce, especially when it's made with Chihuahua cheese, and it's very easy to make.
1 pound Chihuahua Cheese, coarsely grated (Monterey Jack or Asadero will do, but Chihuahua is best.)
1/3 cup half & half or heavy cream
3 tablespoons pico de gallo
Pour half & half into a small sauce pan over low heat. Add cheese and stir until melted. If sauce is thicker than you want, add up to 1/4 cup half & half.
If using pico de gallo, sprinkle it over cheese sauce just before serving. (If you put it into hot cheese sauce, it will cook, and you don't want that.)
Serve over chimichangas, burritos, baked chicken, etc. or use for dipping tortilla chips.