Heat oven to 375 degrees F. Cook macaroni according to package instructions,
or until al dente. Drain, rinse, and set aside.
In large saucepan, sauté onion in butter for two minutes until transparent. Blend
in flour, stirring well to incorporate, and cook for an additional minute. Whisk
milk into butter and flour mixture. Bring to simmer and cook until sauce thickens.
Reduce to low heat and add salt, pepper, hot sauce and mustard. Stir in 2 1/2 cups
Add cooked macaroni to cheese sauce and mix well. Place macaroni mixture in buttered,
ovenproof, 9-inch square dish. Top with remaining 1/2 cup of Cheddar cheese and
Bake for 25 minutes, or until top is golden brown.