Boil a large, salted pot of water for the pasta. Cook pasta al dente according to package instructions.
Add the butter and oil to a skillet over medium-high heat. Once it's hot, add the mushrooms and cook for 5-6 minutes or until the mushrooms release their water and it's cooked off. Take the mushrooms out of the pan and set them aside.
Take the pan off the heat. Add the garlic, Dijon mustard, flour, lemon juice, Italian seasoning, and chicken broth to the pan. Return the pan to the heat. Stir until the mixture is nice and smooth, and let it bubble for a minute or so.
Add in the cream and let it simmer for a couple of minutes.
Add the shrimp and mushrooms to the pan. Cook for 5 minutes or until the shrimp are cooked through and the sauce is thickened to your liking. Taste and season with salt & pepper as needed.
Drain the pasta and toss it with the sauce (add a little pasta water if you wish). Serve with plenty of freshly grated parmesan.