Step 1

Put the pancetta or bacon in a small skillet over medium-low heat. Cook until the fat is rendered and the pancetta is crisp and golden, about 10 minutes. Remove to a paper-towel lined plate.

Step 2

Whisk together the egg yolk, mascarpone or cream and a pinch of salt in a bowl. Zest the lemon into the bowl, then halve the lemon and squeeze the juice from one half into the bowl. Stir in the cheese and black pepper.

Step 3

While the pancetta is cooking, bring 4 quarts water to a boil in a large saucepan or stock pot and season with 2 tablespoons kosher salt. Add the pasta and cook until al dente. Drop the peas into the pot 2 minutes before draining. Scoop out and reserve ½ cup of the cooking water.

Step 4

Put the hot drained pasta back into the pot and toss with the butter until it melts. Whisk ¼ cup of the cooking water into the egg yolk mixture until smooth, then pour over the pasta and toss together with tongs. Drizzle in more water if the sauce seems too thick (keep in mind it will thicken as it sits).

Step 5

Add the pancetta to the pasta and toss gently to disperse. Serve the pasta with additional cheese.