1 tablespoon all-purpose flour
1 cup whole milk, or more if needed
3/4 pound Chihuahua or Monterey Jack cheese, coarsely grated (about 3 cups)
3 tablespoons freshly grated Parmesan cheese
Kosher salt and freshly grated black pepper
Melt the butter in a small saucepan over medium heat. Whisk in the flour and cook for 1 minute. Add the milk, increase heat to high and cook, whisking constantly, until slightly thickened, about 5 minutes. Remove from the heat and whisk in the Chihuahua cheese until melted. Stir in the Parmesan and season with salt and pepper. Thin with additional milk if needed. Keep warm.