Defrost the prawns in cold water. Peel garlic and cut into thin slices. Clean, wash and drain the rocket. Wash lemon, grate dry and cut into slices. Peel prawns, except for the tail fin, and remove the intestines.
Wash shrimps and pat dry. Melt butter in a small pot. Stir in flour and sweat for 1-2 minutes while stirring. Mix fish stock and milk and stir into the flour. Simmer sauce while stirring for about 1 minute, then add cognac and season to taste with salt and some lemon juice (from a crevice). Prepare noodles in boiling salted water with turmeric according to package instructions. Heat oil in a large pan. Put shrimps and lemon wedges in the hot pan and fry for 3-5 minutes, turning occasionally. Season with salt and pepper. Add the garlic 1 minute before the end of cooking.
Prepare noodles in boiling salted water with turmeric according to package instructions. Heat oil in a large pan. Put shrimps and lemon wedges in the hot pan and fry for 3-5 minutes, turning occasionally. Season with salt and pepper. Add the garlic 1 minute before the end of cooking. Drain the pasta. Add rocket to the noodles and serve immediately with sauce, lemon wedges and prawns.