Step 1

If baking, preheat oven to 350 degrees and spray a 9X13 inch baking dish with nonstick cooking spray.

Step 2

Follow the pasta's package instructions and cook pasta, in well-salted water, until al dente. Drain. Set Aside.

Step 3

Beat the egg in a small mixing bowl. Set aside.

Step 4

Melt butter in a large pot, then evenly sprinkle the flour over the melted butter. Whisk together, over medium-low heat, and cook for about 2 minutes or until the mixture becomes a nice golden color, whisking constantly. Don’t allow it to burn.

Step 5

Remove from heat add milk and mustard, and whisk until smooth. Return to medium heat and bring mixture to a boil, stirring constantly. Reduce heat, and simmer, stirring constantly, until sauce is thick about 3-4 minutes. Reduce heat to low.

Step 6

Remove 1/4 cup of the sauce and slowly whisk it into beaten egg, whisking constantly to avoid cooking eggs. Whisk together till smooth.

Step 7

Add the egg mixture to sauce, whisking constantly.  Stir in the cheese and stir until sauce cheese is melted. Add 1/2 teaspoon salt,  1/2 teaspoon pepper and any of the optional seasonings. Taste sauce and adjust seasonings.

Step 8

Add the drained pasta and stir until evenly combined.

Step 9

Serve immediately (very creamy) or pour into prepared baking dish, top with additional 2 cups of shredded sharp cheese. Bake for 20-25 minutes or until the top is golden brown and the casserole is bubbly. Sprinkle top with fresh parsley and serve!