Cook pasta according to the package instruction and drain well.
Shred the Cheddar cheese and tear the American cheese slices into smaller pieces. Set aside.
Make sauce: Mix half and half, butter, salt, pepper, mustard, paprika, garlic powder in a saucepan. Warm for about 2 minutes, but don't let it boil.
Melt cheese: Add all the cheese and stir gently on low heat until the cheese melts. Don't let it become too hot or come to a boil.
Combine: Add drained pasta and stir to coat. Adjust the taste with a bit of salt and pepper if necessary.
Baked version:
Preheat the oven to 350 degrees Fahrenheit (180 degrees Celsius). Butter a baking dish.
Cook pasta for 2 minutes less than indicated on the package; it will continue to cook in the oven. Drain well.
Sauce: Make the sauce as instructed above. Mix with pasta and pour the mixture into the prepared baking dish. Sprinkle with breadcrumbs.
Bake for 15-20 minutes until the dish is golden and bubbly.
Notes
Or any other kind of short pasta like penne, farfalle, rotini, rigatoni, etc.
Or other cheese kinds like Gouda, Gruyere, Jarlsberg Swiss cheese, Colby, or a combination. Add some mozzarella to the mix to make the dish stretchy if you like.