Place a large sauté pan over medium heat. Add the mushrooms to the dry, hot pan, season with salt and pepper, and cook, stirring frequently, until slightly cooked down and starting to color around the edges, about 3 minutes.
Add 1 tablespoon of butter along with the onion, season with salt and pepper, and continue to cook until the onion and mushrooms are golden, 3 to 5 minutes. Stir in the garlic and thyme and cook for 30 seconds to 1 minute. Deglaze the pan with the brandy and allow it to boil away completely.
Remove the mushrooms and onions from the pan and set aside.
With the pan still on medium heat, add the remaining 2 tablespoons of butter to melt, then sprinkle the flour overtop. Stir well to combine and cook for 1 minute to toast the flour.
Slowly stir in the broth and Worcestershire sauce, to taste, and bring the mixture to a simmer. Add the mushrooms and onions back in, turn the heat down to low, and allow the sauce to thicken.
Bring a large pot of salted water to a boil. Cook the egg noodles according to the package directions until al dente. Strain the noodles and divide among four shallow bowls or plates.
Finish the sauce with the sour cream, Parmigiano-Reggiano, lemon juice, parsley, and dill and serve over the noodles.
