Cook meatballs according to package instructions, reserve.
Bring a large pot of salted water to a boil.
Heat a large, heavy-bottomed pot over medium-high heat.
Add butter and olive oil to the pan, add mushrooms and cook, stirring occasionally, until tender.
Add the onion, garlic, and thyme, cook until the onions are translucent and just begin to color.
Deglaze the pan with the red wine, reduce by half, then add the beef stock and Worcestershire sauce, bring to a boil and reduce by ¼.
Combine the vinegar and cornstarch.
While the sauce is cooking, cook the egg noodles according to package instructions, drain, and toss with butter, salt and pepper, if desired.
When the sauce is reduced a bit, whisk in the cornstarch mixture, remove from the heat and stir in the mascarpone, rosemary, and meatballs.
Add the noodles to the pan, stirring to combine and garnish with parsley and scallions. Serve immediately.