Creamy Crock Pot Macaroni and Cheese

Creamy Macaroni and Cheese

8oz uncooked elbow macaroni 
6 tablespoons butter, cut into pieces (divided use)
2 1/2 cups (about 10 ounces) grated sharp Cheddar cheese 
1/2 cup sour cream 
1 (10 3/4-ounce) can condensed Cheddar cheese soup 
1/2 teaspoon salt 
1 cup whole milk 
1/2 teaspoon dry mustard 
1/2 teaspoon black pepper 

Cook the macaroni per package directions.  Drain.  Melt butter in a large bowl in microwave.  Add remaining ingredients. Spray interior of crock pot slow cooker with non-stick spray and add macaroni and cheese.  Cook on low for 1 to 2 hours.  You may sprinkle additional cheese on top if desired.