Creamy Stove-Top Mac-N-Cheese

2 c. elbow macaroni
1 T. butter
2 eggs
3/4 c. milk
1/4 c. plain Greek yogurt
1 t. salt
3/4 t. pepper
3/4 t. dry mustard
1 1/4 c. shredded cheddar cheese
3/4 c. shredded mozzarella cheese

1. In a large pot, boil and cook elbow macaroni according to package directions.  Drain well and return pasta to the pot.  Stir in butter.
2. In a medium bowl, whisk together eggs, milk, yogurt, salt, pepper and mustard.  Pour the egg/milk mixture into the pot and stir.  Add the cheese and continue stirring over medium heat until sauce has thickened and is very creamy {will take a few minutes}.  Serve hot.

Source: http://www.sweetandsavoryfood.com/2013/02/creamy-stove-top-mac-n-cheese.html