In a small bowl, combine Panko and milk. Set aside to soak for a minute.

In a large bowl, mix together the Panko mixture, beef, garlic, egg, Worcestershire sauce, Italian seasoning, salt, and pepper until well combined.

Using a medium cookie scoop, shape the meatballs and arrange them on a baking sheet lined with parchment paper.

In a large skillet, heat 1 tablespoon of olive oil over medium heat.

Arrange the meatballs in one layer and brown on all sides, then remove the browned meatballs to a clean plate.

Pour the remaining 1 tablespoon of olive oil into the same skillet and add the mushrooms.

Cook the mushrooms, stirring frequently for about 3 minutes, or until browned. Remove them to a clean plate.

In the same skillet, melt the butter and stir in the flour. Cook the flour mixture for at least 2 minutes, whisking constantly.

Slowly pour in the beef stock while whisking continuously.

Add Worcestershire sauce and garlic, then bring to a boil, whisking frequently.

Add the browned meatballs and mushrooms, and cook for an additional 8-10 minutes. If the gravy thickens too much, add a little bit of water or stock. Salt and pepper to taste.

If desired, add chopped parsley before serving.