This Pesto Mac & Cheese Shells recipe is a creamy, cheesy twist on a comfort classic with a herby upgrade. Tender pasta shells are coated in a velvety cheese sauce made with garlic, butter, heavy cream, and a trio of cheeses. Pesto adds an earthy, aromatic depth that transforms the dish into something truly special. Finished with a touch of reserved pasta water for silky texture and topped with extra Parmesan, this pasta is cozy and indulgent.