Cook egg noodles al dente in boiling, generously-salted water according to package instructions.

Melt 1 tablespoon butter in a large sauté pan over medium-high heat. Add onions and sauté for 5 minutes, stirring occasionally.

Add the remaining 2 tablespoons butter, garlic, and mushrooms, and stir to combine. Continue sautéing for an additional 5-7 minutes, until the mushrooms are cooked and tender.

Add the white wine, and deglaze the pan by using a wooden spoon to scrape the brown bits off the bottom of the pan. Let the sauce simmer for 3 minutes.

Meanwhile, in a separate bowl, whisk together the vegetable stock, Worcestershire sauce, and flour until smooth.

Pour the vegetable stock mixture into the pan, along with the thyme, and stir to combine. Let the mixture simmer for an additional 5 minutes, stirring occasionally, until slightly thickened.

Stir in the Greek yogurt (or sour cream) evenly into the sauce. Taste, and season with a pinch of salt and pepper as needed.

Serve immediately over the egg noodles, garnished with your desired toppings.