How to make
Chop the onion and fry it in 3-4 spoons of olive oil. Add the mushrooms, cleaned and roughly chopped and a little more olive oil, because they absorb it quickly. Cook for 2 minutes, by stirring at all times and pour the full-fat cooking cream and 1/4 cup of water. Reduce the heat to low and leave the sauce to simmer.
Cook the spaghetti according to the instructions on the package for al dente. When cooking spaghetti, do not break them under any circumstances, but drop them whole, standing upright in the boiling water and spread them out in the shape of a fan. Push the protruding ends and that way all of them will slowly submerge, since the part below that is in the water will soften.
Heat a non-stick pan over high heat - one degree below high. Cut the salmon into scallopini and sear them first on the skin side, then on the other sides briefly, so that the core remains tender. Remove the scallopini and when they cool, gently (so that you don't burn yourself) remove the skin with a sharp knife. It falls off easily, but still use the knife, so that the pieces of fish don't break. Season with salt and set them aside.
Scoop out the cooked al dente spaghetti with a slotted spoon and drop them into the sauce along with some of the cooking water. Add the fat and sauce from cooking the salmon. Add the parmesan and mozzarella, as much salt as you like and tilt the pan to your opposite side and gently toss to mix everything.
Divide the spaghetti into portions and add a piece or two of the salmon and sprigs of fresh basil on each one.
Enjoy your meal!