Instructions:
Preheat oven to 350° F.  Lightly butter a 9 x 13 inch shallow baking dish.

In a small bowl, combine breadcrumbs, 3 tablespoons melted butter and sesame seeds. Set aside.

In a large pot, bring 4 quarts of water to a boil.  Add 1 tablespoon salt and pasta. Cook, stirring occasionally, according to package directions.  Pasta is done when it is slightly chewy to the bite or al dente.  Drain pasta in a colander and set aside.  

Prepare sauce while pasta is cooking.  In a large saucepan over medium heat, melt remaining butter. Stir in onions and sauté 3-5 minutes until softened. Whisk in flour and cook 3 minutes, whisking constantly. Gradually add milk and half and half and bring just to a boil, whisking constantly. Reduce heat and simmer, whisking often, until sauce slightly thickens, 4-5 minutes. Whisk in mustard, horseradish, paprika, salt and pepper. Add cheese and stir until melted.  Remove pan from heat and gently fold in macaroni.  Pour mixture into prepared baking dish and top with breadcrumb mixture.
 
Bake 25- 30 minutes until cheese is bubbly and top begins to brown.
Remove from oven and let rest 5 minutes before serving.

Serves 8
Prep Time: 25 minutes
Cooking Time:  25-30 minutes