Created by CookerKat on August 27, 2015
Step 1: Heat oven to 350°. Butter a 9" x 13"
Step 2: Bring a 4-qt. saucepan of salted water to a boil. Add pasta and cook until only halfway through, about 3 minutes. Drain, rinse under cold water then drain again very well. Transfer to a large bowl. Stir in the cubed cheddar cheese only (not the shredded) and set aside.
Step 3: Combine the salt, 1 tablespoon + 1 tsp. of flour, mustard powder, black pepper, nutmeg, and cayenne in a mixing bowl, then add the sour cream and the eggs and whisk until smooth, then whisk in the half and half, heavy cream, minced onion, and Worcestershire. Pour egg mixture over the cooked pasta and stir to combine. Transfer the mixture to baking dish. Sprinkle 2 cups of grated cheese evenly over the surface.
Step 4: Bake until the pasta mixture is set around the edges but still a bit loose in the center, about 30 minutes. Let cool for 10 minutes before serving.