The beloved Italian pasta cacio e pepe is perhaps best known for two things: being delicious and being frustratingly difficult to cook. At first glance, it looks like a simple recipe, containing only three ingredients: pasta, pecorino romano cheese, and black pepper. But as anyone who has tried to make it will know, the cheese will often clump when added to the hot pasta water, turning what is supposed to be a smooth, creamy sauce into a stringy, sticky mess.