Method
Toast and grind the pepper
Toast the peppercorns in a dry pan over medium heat until fragrant — about 90 seconds. Crack them coarsely in a mortar. You want texture, not powder. Some fine, some chunky. Set aside.
Make the cheese paste
Combine the two cheeses in a bowl. Add 3–4 tablespoons of cold water and work it with a spatula until you have a thick, smooth paste — the consistency of thick hummus. This step is done cold, on purpose. The paste is your insurance against clumping.
Cook the pasta
Boil the pasta in well-salted water but use less water than usual — you want very starchy cooking water. Cook until 2 minutes shy of al dente. Reserve at least 300ml of pasta water before draining.
Build the sauce
Toast the cracked pepper in a wide pan, add a ladleful of pasta water and let it reduce by half. Add the pasta directly to the pan and toss. Take the pan completely off the heat. Add the cheese paste and a splash of pasta water, then toss continuously — the residual heat and the starchy water create the emulsion. Add water little by little until glossy and coating.
Serve immediately
Plate straight away. Add more cracked pepper and a little extra Pecorino. Do not add oil. Do not add butter. Do not add cream. Serve to someone who deserves it.
Why it breaks: Heat is the enemy of the emulsion. If the pan is too hot when you add the cheese, the proteins seize and you get clumps. Off the heat, patience, and starchy water are the fix. If it breaks anyway, add cold water and keep tossing.