Preheat oven to 375 degrees F (190 degrees C). Grease a 9×13-inch baking dish.
Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally until cooked through but firm to the bite, 8 minutes. Drain.
Melt 1/4 cup butter in a saucepan over medium heat. Stir salt and mustard powder into melted butter and remove saucepan from heat.
Whisk milk and cornstarch together in a bowl until smooth; stir into butter mixture until well blended. Return saucepan to stove; cook milk mixture, stirring constantly, over medium heat until sauce is thickened, about 5 minutes. Remove saucepan from heat.
Stir 3 cups Cheddar cheese into sauce until heat from sauce melts cheese. Add pasta to cheese sauce and stir well; pour into the prepared baking dish.
Combine remaining 1 cup Cheddar cheese, gluten-free bread crumbs, 1 teaspoon butter, and paprika in a bowl; sprinkle over pasta mixture.
Bake in the preheated oven until top is crunchy, about 30 minutes.
Gluten-free penne pasta can also be used in place of the elbow. Any variety of cheese can be used in place of the Cheddar cheese, if desired.
You can use your hands or a food processor to turn toast into crumbs for the topping.
If you do not desire a crunchy topping, place reserved 1 cup shredded Cheddar cheese on top of pasta mixture and bake uncovered for 30 minutes.
Source: Read Full Article