INGREDIENTS
1 16 ounce package
elbow macaroni
1/2 tsp
salt
3/4 cup
butter, softened - divided
1 cup
sour cream
1 tbsp
cream cheese, softened
1 8 ounce package
shredded sharp Cheddar cheese
1
egg yolk
2 tbsp
all-purpose flour
1/2 tsp
salt
1/2 tsp
ground cayenne pepper
1 cup
milk
1 8 ounce package
shredded mild Cheddar cheese