Melt 6 tablespoons butter in a large saucepot over medium heat. Add flour and cook, stirring, for 1 minute. Whisk in the warmed milk and bring to a boil, continue to whisk constantly. The mixture will thicken as the heat increases. Continue to stir while adding the dry mustard, nutmeg, cayenne, salt, pepper, hot sauce and Worcestershire. Stir in the 3 cups of Cheddar until it melts.
Pour the cheese sauce over the pasta and add to a 3 quart casserole dish.
Sprinkle the chips, bacon and Parmesan on top and bake for 35 minutes.