1Start with a pan of water over high heat. Once the water is boiling add 2 cups macaroni, cook for about 2/3 of the minimum time. About 6 minutes.
2Combine in a medium crock pot, 1 cup milk, 1/2 cup sour cream, 2 1/2 cups cheese, (I used sharp cheese, use what ever you prefer,) 4 tbsp. butter, 1/2 tsp. salt, pepper, and dry mustard and one can of cheddar cheese soup.
3Drain the pasta well and combine in slow cooker. Mix well. Turn on low.
4Stir the pot about 20 minutes into cooking when the butter is melted, mix well. Stir again several more times. Just a light stir is good.
5It is done when you are getting some browned cheese on the side of the pot and some light browning of some of the pasta on the edge.
About 2 hours. Keep your eye on it, you do not want to over cook. Enjoy.
I also added a small amount of cooked bacon chopped up, for flavour (optional)