In a saucepan, melt four tablespoons of the butter.

Add flour and cook for 2-3 minutes. All the time, whisking it so it will not burn.

Add the milk in a stream, whisking, and bring to a boil.

Add mustard, cayenne and salt and pepper to taste and simmer sauce until thickened, about two minutes.

In a kettle (I used a large pot) of salted boiling water, cook macaroni until just al dente, about 7 minutes and drain well.

In a large bowl, stir together, macaroni, sauce, cheddar, and 3/4 cup Parmesan cheese.

Transfer to a buttered shallow baking dish.

In a small bowl, stir together bread crumbs, paprika and the remaining Parmesan cheese with the remaining 2 Tablespoons of butter, melted.

Scatter evenly over the macaroni and bake in a 350 degree oven for 25 - 30 minutes, or until golden and bubbling.