Place the Italian sausage in a sauté pan over medium heat.
Cook for 4–5 minutes or until the sausage is no longer pink.
Finely chop the sausage into small pieces.
Remove the stems from the mushrooms and wipe off any dirt.
Combine the sausage and Boursin cheese, then stuff into the mushrooms.
Place the mushrooms in a baking dish and bake at 350°F for 25–28 minutes, or until the mushrooms are soft and the cheese is beginning to brown on top.
Let cool slightly and garnish with fresh chopped parsley, if desired.
Serve while still warm.