Stovetop Mac and Cheese

Name: Stovetop Mac and Cheese
Ingredients: 1 cup whole milk; ½ cup heavy cream; ½ teaspoon mustard powder; ¼ teaspoon cayenne pepper; 1 tablespoon cornstarch; 8 ounces cream cheese, room temperature, cut into pieces; 8 ounces medium cheddar cheese, shredded (about 2½ cups); 8 ounces muenster cheese, shredded (about 2 cups); 3 ounces Fontina cheese, shredded (about 1 cup; optional); 1 pound elbow macaroni; Kosher salt