If your beef is not already in slices, slice your beef into thin strips. Coat the strips in a thin coat of flour and allspice. Then, sear the beef in a large pan over medium high heat. Remove the beef from the pan.
1 pound beef, 1 tbsp flour, ½ tsp allspice
Add the sliced onions and sliced brown mushrooms to the pan. Brown them on both sides, ensuring not to overcrowd the pan. Work in batches if necessary. Add garlic in the last minute, and cook until fragrant. Remove onions, mushrooms, and garlic from the pan.
1 onion, ½ pound brown mushrooms, 3 cloves garlic
Add brandy to the pan and cook until it no longer smells like alcohol. Then, remove from the heat, and add Dijon mustard, beef broth, and seasonings. After about a minute of the pan cooling down, add heavy cream and stir to combine. Finally, add sour cream and stir to combine.
¼ cup brandy, 1 tbsp Dijon mustard, ½ cup beef broth, salt, pepper, ½ tsp parsley, ½ tsp oregano, ½ cup heavy cream, ⅓ cup sour cream
Combine flour and water to create a slurry. Add to the sauce and cook until the sauce begins to thicken. This will take a minute or two. If the sauce is too thick, add some beef broth and/or heavy cream to thin it out to your liking. If the sauce is too thin, create a half batch of slurry (of 1/2 tbsp flour and 1 tbsp water) and add to the sauce. Don't forget to allow a minute or two of cook time before judging if the sauce is thick enough. Repeat this process as many times as needed to create a sauce of your desired thickness.
1 tbsp flour, 2 tbsp water
Add the onions, mushrooms, garlic, and beef back to the pan. If they have cooled too much, cook in the sauce for a few minutes to warm through. Then serve!
