Boil a large, salted pot of water for the pasta and cook it al dente according to package directions.
Meanwhile, add the butter and oil to a skillet over medium-high heat.
Add the mushrooms and garlic to the pan and sauté for about 5 minutes, stirring often, until the mushrooms release most of their water and it's cooked off.
Take the mushrooms out of the pan and set aside.
Add the wine, Italian seasoning, lemon juice, flour, and Dijon mustard to the pan. Stir until it becomes a smooth paste.
Stir in the cream and let it simmer for a couple of minutes.
Add the mushrooms back into the pan. Reduce the heat and cook for a few more minutes until the sauce has thickened up a bit. Season sauce with salt & pepper as needed.
Drain the pasta and toss it with the sauce along with the parsley and parmesan if using.