Defrost the prawns if necessary. Wash lemon hot, dry and grate half of the peel. Squeeze the lemon. Peel and chop the onion. Wash parsley, shake dry and chop finely.
Cook the pasta in 3-4 l boiling salted water (approx. 1 teaspoon salt per litre) according to the instructions on the packet. Peel the prawns. Cut lengthwise into the back, remove the dark intestine. Rinse, dab dry.
Wrap each with 1 slice of pancetta.
Heat 1 tablespoon of oil in a saucepan. Fry the onion until transparent. Stir in mascarpone and milk. Stir in lemon zest and juice. Heat, but do not boil! Season with salt, pepper and 1 pinch of sugar.
Heat 2 tablespoons of oil in a frying pan. Fry the pancetta prawns for 3-4 minutes while turning. Drain the noodles. Add the sauce and parsley back to the pot and mix. Arrange the prawns on top.