Preheat oven to 350

In a large pot, boil noodles in salted water until tender

In a mixing bowl, combine eggs, milk, mustard and salt to taste and beat until blended

Drain noodles and return to the pot

Add butter and stir until coated

In casserole dish, add half of the noodles

Layer half of the shredded cheese on top of the noodles

Add the rest of the noodles to the dish

Pour egg mixture over the noodles

Add the remaining cheese to cover the top

Bake covered for 30 minutes

Bake uncovered for 10 to 15 minutes or until cheese is melted and bubbly