In a bowl, combine the panko crumbs and milk.
Add the remaining meatball ingredients to the bowl and mix until everything is evenly incorporated.
Wet your hands and shape the meat mixture into 24 evenly sized meatballs.
Heat a large skillet over medium heat and add oil.
Once sizzling, add the meatballs in batches and fry on all sides until golden brown and cooked through. Don’t overcrowd the pan when frying the meatballs. Add more oil in between batches if needed.
Once the meatballs are cooked through, remove them from the skillet and cover to keep warm.
In the same skillet, melt the butter and whisk in the flour. Cook until golden, whisking consistently.
Slowly whisk in the broth, heavy whipping cream, dijon mustard, salt, and pepper.
Bring the sauce up to a light simmer and cook until it reaches your desired thickness.
Place the meatballs back into the skillet and cook until warmed through.
Garnish the meatballs with fresh herbs and serve over mashed potatoes.