Heat olive oil in a large nonstick pan over high heat.
Toss the beef with flour.
Add it to the pan and sear all sides until browned.
Reduce the heat to low.
Add minced garlic and diced onions to the pan.
Cook and stir for about 1 minute until fragrant.
Add sliced mushrooms and diced tomatoes.
Stir in the Marsala wine and beef stock.
Bring the mixture to a simmer, allowing flavors to meld together.
Simmer the beef mixture until the meat is tender.
Stir in the heavy cream for a rich texture.
Add basil for additional flavor.
Serve the braised beef over cooked tortelloni.
Garnish with extra basil to enhance presentation and flavor.