First chop the onion and mushrooms. Then heat the pan to a high temperature. Cook the pasta according to the instructions on the packet.
In the meantime you can fry the onions in the pan with a little butter until they are translucent. Then add the mushrooms with a little more butter and a dash of water.
As soon as the mushrooms are seared and soft, add the cream. Slowly stir in the pepper, salad spices, balsamic vinegar and stock powder. Let everything simmer for another two minutes.
Now just drain the pasta and serve with the sauce.