Cook your pasta. Bring a large pot, filled about 1/3 of the way up with water to a boil, then add a pinch of salt. Add your pasta and cook until al dente (use your packet as the guide here).
Toast the pepper. Melt the butter in a large, high-sided frying pan over medium heat, then add the crushed black pepper. Cook for a couple of minutes, until smelling lovely and fragrant, then turn the heat off.
Add pasta water to your pepper. Once your pasta is almost cooked, transfer about ¼ cup of pasta cooking water to the pan with the butter and pepper, turn the heat to low and whisk VIGOROUSLY to create an emulsified sauce. You’ll want to essentially shake the pan with one hand while whisking with the other - it will end up looking like a more opaque, glossy sauce. Repeat with another splash of pasta water, then let it simmer for a minute or two as it thickens up.
Add the pasta. Once your pasta is cooked, use tongs to transfer it straight into the pan with the sauce (don’t worry if more pasta water goes in too). Try to arrange the pasta on an even layer in the pan, if you can. Turn the heat RIGHT down, and scatter the grated pecorino all over the pasta, as evenly as possible. Leave it there for about 30 seconds so it starts to melt from the residual heat on the pasta. This is key for creating a silky smooth sauce.
Toss the pasta through the sauce. Once it’s started to melt, use the tongs to toss the pasta vigorously again, until you have a lovely thick, emulsified cheesy, peppery sauce. If it’s a bit thick, you can add a splash more pasta water. Divide between plates, then enjoy right away.