Bring a large pot of water to a boil for cooking the pasta.
Heat a skillet over medium to medium- high. Add the olive oil, two turns of the pan. Add the pancetta and stir 2 minutes. Add the onion and garlic, stir to soften a few minutes more, then add the wine and cook until the wine evaporates. Add the stock and bring to a bubble. Add the cream and reduce the heat to medium-low. Add the peas; season with salt and pepper.
Salt the boiling water, add the pasta and cook to al dente. Reserve 1/2 cup of the starchy cooking water; drain the pasta.
Stir the mascarpone, lemon juice and the cooking water into the pea mixture until a sauce forms. Toss with the penne and season. Serve the pasta in shallow bowls topped with a little pecorino, mint and parsley.