Make It
Step 1
Cook pasta according to package directions. Drain, reserving 1 cup cooking liquid.
Step 2
Return pasta to pot set over low heat; add reserved cooking liquid, sour cream, butter, bouillon, mustard and pepper until well coated and creamy.
Step 3
Stir in cheddar, mozzarella and Parmesan cheeses; heat over low heat for 3 to 5 minutes or until cheeses are melted and sauce is thick and creamy. Serve.