To shave the asparagus stalks into long ribbons, place a stalk on the cutting board in front of you with the tip pointing away from you. Starting at the stem end, use a Vegetable Peeler to shave ribbons off the stalk, pressing down to ensure you get an even cut.
Bring a large pot of water to a hard boil, add in the pasta, and a pinch of salt, and boil until al dente. ~5-8 minutes (depending on the type of noodle).
In a large skillet over medium heat add the olive oil until hot. Add in the shallots and garlic. Sauté until translucent ~5-6 minutes. Add in the black pepper and red pepper flakes.
Drain the pasta but reserve 1-2 cups of the pasta water. Pour a cup of pasta water and lemon juice into the skillet and add mascarpone. Stir until dissolved. Add in the shredded parmesan cheese and stir.
Toss in the asparagus ribbons for a few minutes to soften slightly. Add the pasta to the pan and gently mix. Add the prosciutto and remove the pan from the heat, gently stirring in the prosciutto. Taste and adjust seasonings. Plate and add shaved Parmesan on top.