For the spaghettini with leeks and grilled shrimp, first grate the lemon peel, squeeze the lemons. Rinse and clean the leeks, cut lengthwise into thin strips.
Melt butter, sweat flour in it. Deglaze with whipping cream. Stir sauce until smooth. Add lemon juice and zest. Season finely with salt, pepper and nutmeg. Bring the lemon sauce to a gentle simmer. Preheat broiler.
Cook spaghettini in enough salted water until al dente, about 8 minutes. Add leek strips after 4 minutes and cook.
Meanwhile, rinse shrimp and coat with oil. Grill on both sides for about 3 minutes.
Drain spaghettini and leeks, drain well. Serve spaghettini with leek and grilled shrimp.