Gather all ingredients. Preheat oven to 350°F. Grease a baking dish with 1 tablespoon of the melted butter.

Stir crackers and 3 tablespoons of melted butter in a skillet; cook over medium until toasted.

Whisk flour and 4 tablespoons melted butter in a Dutch oven over medium until bubbly, about 2 minutes.

Gradually add milk and half-and-half, whisking constantly, until it coats a spoon lightly, 2 to 4 minutes.

Remove from heat; whisk in mustard, salt, garlic powder, paprika, and bouillon.

Gradually whisk in cheeses until melted and smooth.

Stir in cooked pasta until evenly coated. Spread half of the mixture into the baking dish. Top with mozzarella and Colby Jack.

Dollop and spread sour cream evenly over the mixture, then add the remaining pasta and cheeses.

Sprinkle cracker mixture evenly over the dish.

Bake in the oven until bubbly and browned, about 25 to 30 minutes.