Add Buttermilk to Your Boxed Macaroni and Cheese

When I make macaroni and cheese from the (blue) box, I rarely stray from the instructions. As far as processed foods go, this one is pretty dialed in, and I’m not one to mess with aggressively orange perfection. But the other night, after two martinis and a shot of Fernet, I remembered I had buttermilk in my fridge,…