Cook the Pasta: Start by cooking your elbow macaroni in salted water according to the package instructions until al dente. Drain and set aside.
Prepare the Cheese Sauce: Heat the milk and heavy cream in a large saucepan until hot but not simmering. Grate the American cheese on a cheese grater or cut it into cubes. You can also have the deli slice it into sandwich squares and add them in 2 at a time.
Add the Cheese: Lower the heat and stir the American cheese into the warm milk. Continue stirring until the cheese is fully melted and the sauce is smooth. Season with garlic powder, dry mustard, hot pepper sauce, and Worcestershire.
Mix the Pasta and Sauce: Combine the drained noodles and cheese sauce in a glass casserole dish, stirring gently to ensure the pasta is well coated. Fold in the roasted green chiles.
Bake: Bake at 375° for 20 minutes or until hot throughout.
Top with Cheese: Turn on the broiler in your oven. Top with the 1 1/2 cups shredded melting cheeses and broil just until the shredded cheese is melted.
Serve: Remove from the oven and serve hot and fresh.