In a bowl, combine the ground beef, ground turkey, breadcrumbs, minced parsley, finely grated garlic, grated-and-chopped onion, egg, chili flaked, and a generous pinch (or two) of salt.
Mix throughly with your hands and form 1"-1 1/2" meatballs. Place on the side, while you prep the rest of the ingredients for the sauce.
In a wide pan over medium heat add a heavy drizzle of olive oil. Once hot, place the meatballs in and sear for about 2 minutes, or until lightly browned. Flip and sear for another 2 minutes.Remove the meatballs and place on the side.
Reduce the heat to medium-low and add in the butter. Once melted toss in the sliced mushrooms, toss to coat, sprinkle with a pinch of salt and cook undisturbed for 2-3 minutes. Stir, and continue cooking for another 1–2 minutes.
Add in the onions, garlic, and thyme and cook for another 2-3 minutes
Toss in the flour and stir continuously for 1 minute to form a slurry.
If enjoying right away start cooking the egg noodles as per packaging in salty water.
Pour in the beef broth, Dijon mustard, and a few cracks of fresh black pepper. Whisk to combine the slurry with the flour and simmer on low uncovered for 5-7 minutes. The sauce will start to thicken.
Stir in the heavy cream and mix to combine. Add the meatballs back to the pan and simmer uncovered for another 5–7 minutes.
Once cooked through, remove from the heat, add in the cooked egg noodles and toss to coat.