SWISS MAC & CHEESE WITH SMOKED SAUSAGE

~ Eat at Home

4 T. butter

1/2 onion, diced

1/4 c. flour

3 c. milk, warmed

1 T. Dijon mustard

2 c. shredded Swiss cheese

1 lb. smoked sausage, sliced and fried

1 lb. pasta shells, cooked

Melt butter over medium heat. Add onion, cooking until soft.  Whisk in flour and cook for one minute.  Whisk in milk, stirring often until well blended.  Add mustard and cheese. Once cheese has melted, combine sauce with cooked pasta and sausage.