Put water on for the pasta and when it’s boiling add a decent amount of salt and then, when it’s boiling again, the spaghetti. Italians say the water pasta cooks in should be as salty as the Mediterranean.Cut the rind off the pancetta (or guanciale if you’ve been able to get it) and put the rind in the pan with the oil on medium to high while you dice the rest of the pancetta. Then add it and fry for about 5 minutes, maybe more, until it is beginning to crisp. Remove the rind (I like to eat it, but you may not feel the same way.) Throw in the vermouth and let it bubble away for about 3 minutes until you have about 2 teaspoons or so of syrupy wine-infused bacon fat. Remove from the heat.For the egg mixture, simply beat the yolk, the whole egg, the cheese, the pepper and the nutmeg (the pancetta and the cheese should provide enough salt) together with a fork. When the pasta’s ready, quickly put the bacon pan back on the heat, adding the butter as you do so. Remove a cupful of pasta-cooking water and then drain the spaghetti and tip it into the pancetta pan. Mix it well together, then turn off the heat (take the pan away from the hob if your stove’s electric).Pour the egg mixture over the bacony pasta and quickly and thoroughly turn the pasta so that it’s all covered in the sauce. Whatever you do, don’t turn the heat back on or you’ll have scrambled eggs; in time, the hot pasta along with the residual heat of the pan will set the eggs to form a thickly creamy sauce that binds and clings lightly to each strand of pasta. Add a tablespoon or so, going gently, of the pasta cooking water as you toss it all together. This will help make the sauce creamier. This makes two platefuls: it’s up to you whether you conclude this is enough for one or two of you.