Combine the ingredients for the meatballs first. Set the mix to the side for 10-15 minutes so that it comes together and the meatballs are easier to form. After the time, roll the meatballs by hand.
In a pan on medium high heat, add a little oil for cooking then sear the meatballs on 1-2 sides then remove from the pan. They will finish cooking in the sauce.
Once the meatballs are seared, add in the mushrooms. Allow the water to release from the mushrooms. Once the mushrooms start to sear, add a little oil and sear them until they are browning.
Next, lower the heat to medium then add in the butter. Once the butter is melted add in the flour then stir the flour with the mushrooms for about 1 minute.
Now, add in the dijon mustard to combine with the flour and mushrooms. Next, pour in the beef broth. Followed by the Worcestershire sauce, onion powder and beef bouillon cube. Allow to simmer and thicken while stirring. Carefully taste the gravy to see if you want more salt. Add a little pepper to taste.
Add back in the meatballs, lower the stove top to low then cover the pan. Allow the meatballs to simmer until fully cooked through.
Once they are cooked through, turn off the heat. You're now ready to serve, enjoy!