In a large skillet, heat olive oil over medium-high heat. Add the ground beef, salt, and pepper. Cook until no longer pink (breaking apart and occasionally stirring).
Turn off the heat, and transfer the beef to a bowl. Cover, and set aside.
Return the heat to medium-high, melt the butter, and add the onions and mushrooms. Cook about 3-5 minutes, or until onions are translucent.
Stir in the garlic and flour, and cook until fragrant, should take less than 1 minute.
Add the wine, and cook about 2 minutes, using the spatula to scrape any browned bits off the bottom of the pan.
Stir in the beef broth, Worcestershire, and dijon. Bring to a simmer, then reduce heat to medium-low and simmer about 5 minutes.
Add the greek yogurt and cooked beef, stir and remove from heat.
Season with salt & pepper to taste (I added ¼ teaspoon each).
Sprinkle with a handful of chopped parsley, and serve over egg noodles or rice.