Estelle's served this Mac N' Cheese at Luke's 4th birthday party and I will say, nothing was left over for the next day! Gone, baby gone!!
Preheat the oven to 350 degrees F. In a large bowl, toss together the pasta with the cheese cubes and pour into the baking dish. In a large bowl, mix together the flour, salt, black pepper, cayenne pepper, dry mustard, nutmeg. Add the sour cream, egg, evaporated milk, half-and-half and onions. Pour over the pasta and cover with the shredded Cheddar. Bake uncovered until the top is just beginning to brown, about 35 minutes. Meanwhile, in a skillet over medium heat, melt the butter, add the bread crumbs and sautee’ until golden. Sprinkle the bread cubes on top of the macaroni and cheese and bake until golden brown, about 10 minutes more.