Instructions:
Bring water that has been salted with one teaspoon of salt to a boil in large cooking pot. Add elbow macaroni and cook until just done. Drain and set aside.

In small skillet, melt 1 tablespoon of the butter. When melted add chopped onions and cook until almost translucent, approx. 5 minutes over medium heat. Spoon onto paper towel to drain, and set side.

Next melt remaining butter in large size pot. When melted whisk in the flour, mustard, and horseradish. Continue whisking for at least five minutes over medium heat. Keep whisking to avoid lumps. Slowly add milk and half and half. Next add the onion and paprika. Turn heat to low and cook 5 more minutes. Stir occasionally. Stir in half of the cheese. Add salt and pepper. Fold in the macaroni, and gently add one half of the remaining cheese. Pour into a 2-quart casserole dish. Top with remaining cheese.

Bread Crumb Topping: Sprinkle panko breadcrumbs on top of macaroni and cheese. Melt the butter and poor evenly on top of crumbs. Sprinkle sesame seeds evenly over crumbs. Bake for 30 minutes at 350 degrees. Remove from oven and rest for five minutes before serving.

Serving Size: 8+