Macaroni and Cheese

With milk approaching $4.00 a gallon, I want to use every last bit. Unfortunately, there are a few cups of my gallon left and they're beyond cereal, but not too far gone. I think it will make macaroni and cheese just fine at this stage.

I've heard, now that I'm a transplant, that the base of macaroni and cheese varies. In the north, people make a simple white sauce and add cheese. In the south, evaporated milk is invited. The first recipe I ever tried that wasn't Kraft from a box involved a white sauce, and the first time it came out great. The second time I had a little too much confidence and burned the sauce, and I'm sure the more experienced among you know there is no recovery from that.

This is the recipe I'm trying. Spike is napping in the stroller at the moment; I hope it goes well.

Baked Macaroni and Cheese
2 tbsp butter
2 tbsp all-purpose flour
2 cups milk
1 cup sour cream
3/4 tsp salt
1/2 tsp dry mustard
1/4 tsp ground black pepper
1 (8 oz) pkg elbow macaroni
2 cups shredded sharp Cheddar cheese
1 cup shredded cheddar of choice for topping

Preheat oven to 350. Melt butter in a saucepan over medium heat. Stir in flour and cook 1 minute, stirring constantly. Stir in milk, sour cream, salt, mustard and pepper; cook, stirring frequently, until mixture boils and thickens. Meanwhile, bring a pot of lightly salted water to a boil. Add macaroni and cook for 8-10 minutes or until al dente; drain. To the milk mixture add the cheese; stir until cheese melts. Combine macaroni and cheese sauce in a 9x13 baking dish; mix well. Top with extra cheese. Bake for 30 minutes, or until hot and bubbly. Let cool 10 minutes before serving.