2–3 tablespoons grated Parmesan, plus extra for serving
¼ cup finely sliced shiso leaves (or mint, if unavailable), plus more for garnish
Combine oil and 1 ½ tablespoons minced garlic in a small skillet or saucepan. Cook over low heat, stirring occasionally, until garlic is pale golden brown, 9 to 12 minutes. (For me, this took the full 12 minutes — the garlic began to sizzle gently at around 4 minutes or so, and took about 8 minutes at a gentle sizzle to turn golden.)
Meanwhile, bring 2 quarts of water to boil in a large pot. Add the orecchiette and 2 teaspoons salt and cook, stirring frequently, until al dente. (The pasta should still have quite a bit of bite; it will continue to cook in the sauce, so I prefer to take it off the heat when it’s several minutes less cooked than I want.)
Reserve 1 cup of the starchy cooking water, then drain the pasta and return it to the pot. Add the peas, lemon zest and juice, reserved garlic-oil mixture, and ¾ cup of the pasta water to the pasta. Stir until pasta is well-coated with oil and no water remains in the bottom of the pot.
Add the mascarpone, Parmesan, and shiso leaves. Toss until the cheeses melt and evenly coat the pasta. If needed, loosen the pasta with the remaining ¼ cup pasta water. Season with more salt and plenty of black pepper to taste, then serve, with extra Parmesan on the side and more shiso, if desired. Enjoy!