Cacio e pepe is the Roman (and, dare I say, better) answer to macaroni and cheese. It's traditionally made with pecorino Romano, a salty sheep's milk cheese, and abundant ground black pepper. Take a few measures to prevent the sauce from clumping: first, use the finest grater you have to grate the cheese so it can melt readily. Next, encourage an emulsion in the pan by swirling together the pepper, oil, and starchy pasta water until it comes together. And finally, if your pan isn't roomy enough to toss the pasta, place everything in a big bowl and toss with tongs, adding a little pasta cooking water at a time, until the sauce comes together.