Cook the pasta in plenty of generously salted water according to the packet’s instructions.
While it cooks, prepare the ingredients for the sauce, but only start to cook the sauce about 2 minutes before the pasta is cooked, as you will need some of the cooking water.
Cut the fish into small pieces, finely chop the garlic, set aside in a bowl. Squeeze the lemon juice. Grate the Parmesan. Chop the herbs.
Drain the pasta and keep about ½ - ¾ cup of the cooking water.
Heat the oil in a large pan. Add salmon cubes and garlic and stir for 1 minute.
Add crème fraiche, cream, scant ½ cup pasta water, lemon juice, Parmesan, salt, and pepper. Stir well for one minute on low heat.
Add the drained pasta and stir well for about 1-2 minutes to coat with the sauce. Add an extra splash of pasta water if necessary.
Stir in the herbs and adjust the taste with more salt, pepper, or lemon juice.