Heat the oven to 375°F. Lightly grease 8 cups of a standard muffin pan.
Cook the macaroni in a saucepan of boiling water according to the package directions until just tender. Drain it well and let it cool slightly.
In a large bowl, whisk together the egg, milk, ketchup, garlic powder, salt, and black pepper. Stir in the breadcrumbs, then add the ground beef, diced ham, cheddar, and cooked macaroni.
Mix gently with clean hands or a fork just until everything is evenly combined. Avoid pressing the mixture too firmly, which can make the muffins dense.
Divide the mixture among the 8 prepared muffin cups, pressing it lightly into each cup. Bake until the centers reach 160°F, about 25 to 30 minutes.
Let the muffins rest in the pan for 5 minutes, then loosen the edges and lift them out to serve.