Heat oil and butter in a large skillet over medium high heat.

Meanwhile, in a small mixing bowl, combine the beef, sausage, egg, mayonnaise, pork rinds, parmesan, and salt and pepper.

Form mixture into large meatballs, about 1-2 Tablespoons each.

Cook meatballs in skillet for 8-10 minutes.

Once the meatballs are cooked, remove from the pan and set aside.

Add diced onions to the same skillet in which you cooked meatballs, sautéing until onions are browned all over, turning every 2 minutes.

When onions are translucent, add the garlic and mushrooms. Cook for 2 minutes, then add the beef broth.

Stir in the sour cream and dijon mustard, and a bit of Worcestershire sauce, to taste.

Add the meatballs back in and allow the gravy to cook and thicken, 3-5 minutes.

For a thicker gravy, remove 1/2 cup of the sauce from pan place in a small mixing bowl. Whisk a Tablespoon of arrowroot powder into that sauce, then pour back into the skillet and stir to mix.

Season to taste with salt and pepper and garnish with parsley.