Heat 2 tbsp. of olive oil in a pan, toss in the shrimp and quickly brown for about 2-3 minutes. Set aside.
Clean the leeks discarding the top green part. Slice and rinse repeatedly in cold water to eliminate any trace of dirt. Drain well.
Heat the remaining olive oil in another pan, add the leeks and stir them over moderate heat until they become soft. Add the chopped onion and keep on stirring for another 5 minutes. Then add the butter and the chicken stock. Three minutes later add the shrimp and cook for a few more minutes. Add salt and freshly ground pepper to taste.
Cook the fresh tagliatelle in salted boiling water. Stir with a wooden spoon. Because the tagliatelle are fresh, they will be cooked by the time the water returns to a boil (about 2 minutes).
Drain, place in a pre-heated platter or bowl, toss in the leek and shrimp sauce with some of the cheese. Serve, bringing the rest of the Pecorino Romano to the table in a separate bowl.
Serves 4
