Preheat oven to 400 degrees. Blend together the salt, pepper, sugar, and mustard powder. Next, boil elbow macaroni noodles to al dente, drain and pour into the baking dish. Toss the noodle with half of the spice mix, mild and sharp cheddar, and butter.
Whip softened cream cheese in a mixing bowl until creamy. Add eggs and mix until pale yellow and smooth.
In a cold saucepan or pot, pour the cream cheese egg mixture followed by the half and half. Stirring constantly, turn the flame to low heat then add the Swiss and gruyere cheese, remaining spice mix, and butter. Allow cheeses to melt slowly stirring constantly. Continue stirring until the sauce thickens and resembles a thin custard. You will notice that the cheese will become soft and stringy. Remove the pot from the heat source.
Immediately pour the cheese sauce over the noodles and cheese. Stir to mix well. Bake uncovered for 30-40 minutes. The sauce will be absorbed by the noodles and the top will be a golden brown. Let it sit for 10 minutes before serving.
Be sure to assemble and bake on a cookie sheet because the cheese sauce may overflow a little.