Creamy Stovetop Macaroni and Cheese

elbow macaroni½ cup (113 grams) unsalted butter¼ cup + 2 tablespoons (53 grams) all-purpose flour5 cups (1.2 liters) whole milk24 ounces sharp cheddar cheese, shredded8 ounces American cheese, sliced and choppedSalt and pepper, to taste