Season steak with salt and pepper. Heat butter and oil in a large pot or dutch oven over medium-high heat. Brown steak in the pot for 2-3 minutes turning once or twice. Cook in 2 batches if needed to avoid overcrowding the pot. Remove to a clean plate and set aside.

Reduce heat to medium. Add another Tbsp of butter if needed and the diced onion and sliced mushrooms to the pot. Sauté 5 minutes or until tender. Add garlic and stir for 30-60 seconds until fragrant. If using brandy, pour in and scrape up any bits stuck to the bottom of the pot. (Be very careful pouring flammable brandy in! Turn burner off if using an open flame.)

Bring a pot of water to boil over high heat for the egg noodles. Meanwhile, add the browned steak and any juices back to the pot. Pour in beef broth and scrape any bits still stuck to the bottom. Add beef bouillon and bring to a boil. Cover and reduce heat to a simmer. Cook for 5 minutes, or until beef is cooked through. Boil the egg noodles while soup is simmering, following the package directions. Carefully drain when cooked and set aside.

Slowly stir in heavy cream and sour cream into the soup. Heat on low for a couple of minutes until warmed. Dish up a serving of noodles into a bowl and ladle the beef stroganoff soup over top. Serve with crusty bread and enjoy!