Preheat oven to 350°F. Butter a 9×13-inch baking dish and set aside.
Cook macaroni in salted boiling water for 2 minutes less than al dente. Drain and set aside.
Grate 6 cups of cheddar, reserving 1 cup for topping.
Melt butter in pot over medium heat. Stir in flour and cook for 1–1.5 minutes until golden.
Gradually whisk in milk, ½ cup at a time, until smooth. Bring to a gentle boil.
Reduce heat and whisk constantly until sauce thickens, 5–7 minutes.
Remove from heat. Stir in 5 cups cheddar, salt, and pepper until melted.
Mix cooked macaroni into the cheese sauce.
Spread half the mac and cheese into prepared dish. Sprinkle with half the reserved cheese. Repeat.
Sprinkle with paprika if using. Bake uncovered until bubbly and golden, about 10 minutes.
