Preheat your oven to 400°F (200°C) and prepare a baking sheet lined with parchment paper.

In a mixing bowl, combine ground turkey, breadcrumbs, onion, garlic, egg, milk, salt, and pepper. Mix until well combined.

Form the mixture into small meatballs (about one inch in diameter) and place them on the baking sheet.

Bake for approximately 20 minutes until golden brown and cooked through.

For the sauce, melt butter in a saucepan over medium heat. Whisk in flour until bubbly. Gradually add beef broth and simmer until thickened. Stir in sour cream before serving.

Serve the meatballs drizzled with the sauce and garnish with parsley if desired.