Boil your pasta in salted water as per the package instructions
Save 1 cup starchy pasta water, then drain
Toast peppercorns in a dry pan (2 minutes) and crush coarsely
Add butter and let it melt, then whisk in half a cup of pasta water and simmer
Remove from heat, stir in cheese and pasta.
Mix well, adding in extra water until the sauce is silky and clings to the pasta