Cook the pasta in a large pot of boiling water until quite al dente (it will finish cooking in the sauce).
Meanwhile, melt the butter with the oil in a large frying pan on medium-high heat and sauté the onion until soft. Add the garlic and sauté another minute.
Add the mushrooms and cook until soft. Season well with salt and pepper.
Add the wine and cream, simmer for 5 minutes, then add the parsley and check the seasoning again.
Toss the pasta through the sauce, sprinkle with Parmesan cheese, and serve.
To clean the mushrooms, use a damp paper towel or a dishtowel to remove any dirt one at a time. Cleaning mushrooms with water will make them waterlogged. Mushrooms absorb water like little sponges and they won't brown well when cooked if they are full of water.
If you feel you must use water, you can lightly rinse the mushrooms with cool water and pat dry with paper towels, but do not soak them.
When cooking mushrooms, don't overcrowd the pan. Cook mushrooms in a pan with a good amount of surface area. You want to be able to spread the mushrooms in a single layer to allow contact with the hot pan and let moisture evaporate quickly so they brown nicely.