Bring a large pot of salted water to a boil over high heat. Add the pasta and cook until just short of al dente, 10 or 11 minutes.
Meanwhile, heat a large straight-sided skillet over medium heat. Add the butter and olive oil to the hot skillet. When the butter is melted, add the garlic; cook, stirring often, until soft and fragrant. Add 1/2 cup of the pasta water, then reduce the heat to low.
When the pasta is ready, lift it out of the water and add it directly to the sauce; reserve the pasta water. Sprinkle the Parmesan over the pasta and stir to combine. Return the heat to medium, add the mascarpone, lemon zest and 3/4 teaspoon salt and toss well. Continue cooking until the pasta is al dente, another minute or two, adding pasta water as needed to thin the sauce.
Add the peas and lemon juice; toss well to combine. Add more pasta water as needed to reach the desired sauce consistency (you will most likely use about 1 1/2 cups pasta water in all).
Sprinkle with the pink pepper and additional Parmesan, if desired.