Start by drying the beef with paper towels. Place the meat in a medium bowl. Coat the steak with the flour and lots of salt and pepper. Set aside.

In a large pan, heat 1/4 cup of the butter over medium high heat until melted. Sear the beef until browned on all sides. Don't overcrowd the pan, or the meat will steam instead of brown! You can sear in batches if necessary. Once the beef is nice and browned, transfer it to a plate.

Melt another pat of butter in the skillet over medium heat, and add the shallots and mushrooms (if using). Saute, stirring frequently, until the veggies are golden brown, about 5-7 minutes. Stir in the garlic and saute until fragrant. Then, add the beef along with any juices back into the pan.

Deglaze the pan with the brandy, and let it reduce until there are only a couple of tablespoons left (it may thicken a little). Add the beef broth, bay leaf, mustard, thyme, salt, and pepper. Let the beef simmer for at least 1 hour, preferably 1 1/2 hours, to tenderize the meat.

Meanwhile, cook the egg noodles (or rice) according to package directions. Stir in a pat of butter and couple pinches of salt.

When the beef is done simmering, stir in the half of the sour cream. Taste, and add more sour cream, 2 Tablespoons at a time, until it's to your desired consistency. Cook for about 5 more minutes to heat. Garnish with parsley and serve the stroganoff over noodles or rice.