Bring a large pot of water to a boil for the pasta.
Heat 1 tablespoon EVOO in a large skillet over medium-high heat. Add 3 tablespoons butter and melt until it foams. Add mushrooms and brown about 12 minutes until golden. Add shallots and season with thyme, salt and pepper. Stir 3 minutes more, sprinkle in flour, add marsala and reduce 1 minute. Add stock and cream, and simmer to thicken a couple minutes more.
Meanwhile, melt remaining butter in EVOO in a medium skillet. Add breadcrumbs and garlic, and brown until nutty and fragrant. Remove from heat, let cool a couple of minutes then add cheese and parsley, and season with black pepper.
When you add shallots to mushrooms, drop fettuccine and cook to al dente, 8-9 minutes. Reserve a little starchy cooking water, drain, toss with sauce and serve topped with breadcrumbs.