serves: makes enough sauce for 1 pound of pasta
1½ sticks of butter, or more to taste
10 fresh whole sage leaves
¼ teaspoon freshly ground black pepper, or to taste
hot water, from the pasta-cooking pot
1 cup Parmigiano-Reggiano, grated
Melt the butter in the pan over medium heat, lay in the sage leaves and heat until the butter is sizzling gently. Toast the leaves for 1 minute or so.
Ladle in 1 cup boiling pasta water; stir the sauce and simmer for about 2 minutes and reduce liquid by half before adding pasta. Grind the black pepper directly into the sauce.
Keep the sauce hot over very low heat; return to a simmer just before adding pasta
Finish cooked pasta and sauce in the skillet. Off the heat, toss in the cheese just before serving.