Place ground beef in a large skillet over medium heat. Start to break it up and season with salt and pepper. Crumble and brown ground beef for about 7 minutes. Remove the beef from the pan, set aside and wipe extra grease out of the skillet.

Heat oil over medium-low heat in the same skillet and add the diced onion and minced garlic to the skillet. Allow that to saute for a couple minutes and then add the mushrooms to the pan

Saute sliced mushrooms for 5 minutes tossing frequently. Season with a pinch of salt.

Place butter in the skillet and allow it to melt completely. Sprinkle flour into skillet and toss so that it makes a paste with the butter and mushrooms.

Slowly pour the heavy cream and beef broth into the skillet, stirring as you pour so that the flour and butter paste dissolve into the liquid. 

Mix the sour cream and dijon into the sauce and then pour the ground beef crumbles back into the pan.

Let the whole thing simmer for about 5 minutes then serve over egg noodles.