Add all the meatball ingredients (except for the olive oil) to a fairly large prep bowl. Using your hands, mix it together and then form 1 ¼ - 1 ½-inch meatballs (use about 2 ½ tbsp meat/meatball and it'll make approx. 25-30 meatballs). Place the meatballs on a parchment-lined baking sheet for easy clean-up.

Add the olive oil to a large and deep skillet or a Dutch oven/pot and let it heat up for a few minutes over medium-high heat. Fry the meatballs in two batches until all sides are browned (about 5-7 minutes/batch). It's easiest to turn the meatballs with tongs. You may need to add a splash more oil for the second batch. Transfer meatballs to a plate.

Pour out most of the fat from the skillet, but keep the browned bits in for extra flavor (don't wipe it out).

Reduce the heat to medium and add the butter to the skillet. Once it’s melted, stir in the flour and cook, stirring often, for a few minutes until the roux starts to turn golden.

Slowly whisk the beef broth in, and ensure the flour has dissolved into the sauce.

Whisk in the Dijon mustard and Worcestershire sauce.

Add the meatballs back to the pan and cook for about 10 minutes or until the meatballs are cooked through and the gravy thickens to your liking (it's not meant to be a super thick gravy).

Turn off the heat and stir in the sour cream. I add it right into the skillet, but you could take out some of the sauce and add it to a cup and mix the sour cream in there first if that's easier for you.

Season with extra salt & pepper as needed. Sprinkle with fresh parsley and serve immediately.