Method:
Put the water in a pan to boil (put about half of what you usually use to cook the pasta, so it will be richer in starch) and when it boils you can add salt to taste. Once salted, you can cook the spaghetti.
Pour the black peppercorns into a large non-stick pan, toast it over low heat, stirring with a wooden scoop, then blend with a couple of ladles of pasta cooking water.
Drain the spaghetti when they are very al dente (keeping the cooking water aside) and pour them directly into the pan with the toasted pepper. Stir the pasta constantly and add a ladle of water or two as needed to continue cooking. Continue to pour a ladle of water only when needed (when you see that the pan is almost completely dry) and stir with the kitchen tongs.
In the meantime that the pasta is cooking, take care of the cheese cream: pour about half a dose of grated cheese into a bowl. Add a ladle of pasta cooking water. Stir with a whisk and add more water as needed. Then add the remaining dose, keeping a little aside to season later.
Add a little more water as needed: at this stage you will need to carefully calibrate the amount of cheese and water to obtain a cream of the right consistency. Finish cooking the pasta, adding a little more hot water if necessary. Turn off the heat of the pan with the spaghetti and pour the cheese cream.
While you pour the cheese cream on the spaghetti, move them continuously with the kitchen tongs, stir and toss the pasta again then serve your spaghetti with cacio e pepe and season with the remaining pepper, decorate with other grated cheese!