Macaroni and Cheese with Caramelized Onions and Bacon

Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally, for 8 minutes (noodles will still be slightly hard). Drain. Transfer to a large bowl; add 4 tablespoons butter and toss to coat.

Whisk sour cream, cream cheese, and egg together; stir into macaroni. Stir in 3 cups each Asiago cheese and Cheddar cheese.

Cook bacon in a large, deep skillet over medium-high heat, turning occasionally, until evenly browned, about 10 minutes. Reserve drippings in skillet. Transfer bacon to a paper towel-lined plate to drain, then chop into small pieces.

Preheat the oven to 400 degrees F (200 degrees C). Grease a 9x13-inch baking dish.

Add onion, 2 tablespoons butter, and garlic to drippings; cook and stir over medium-high heat for 2 minutes. Reduce heat to medium-low. Add brown sugar; cook, stirring occasionally, until onion very soft and golden brown, 10 to 15 minutes. Stir in bacon, parsley, and panko bread crumbs; transfer to a small bowl and set topping aside.

Heat same skillet over medium-low heat. Add remaining 2 tablespoons butter; melt. Whisk in flour; stir until light golden brown and becomes paste-like, about 5 minutes. Gradually whisk in milk and bring to a simmer over medium heat. Cook and stir until smooth and thickened. Stir in hot pepper sauce, ground mustard, paprika, pepper, and salt. Remove sauce from heat; let cool 5 minutes.

Pour sauce over macaroni mixture, stir to coat. Transfer to the prepared baking dish; sprinkle with remaining 1 cup each Asiago cheese and Cheddar cheese. Top with bread crumb topping.

Bake in the preheated oven until hot, bubbling, and golden brown on top, about 30 minutes.