1. Wash and drain the spinach. Slice the onion and garlic. Cut the mushrooms into slices.
2. Heat a pan with olive oil. Brown the salmon fillets for 3 to 4 minutes on each side, then set aside.
3. In the same pan, sauté the onion, garlic, and mushrooms for 5 minutes. Add the spinach and let it wilt.
4. Pour in the heavy cream, season, and simmer for 3 minutes.
5. Return the salmon to the pan and let it warm up for 2 minutes.
6. Serve the cooked salmon with creamy spinach sauce.
7. Serve the cooked salmon with creamy spinach sauce.