Melt 2 tablespoons of unsalted butter in a skillet over medium-low heat. Add the onions and cook for about 15 minutes until very tender but not browned. Remove from heat and allow to cool.

In a food processor, combine the cooked and cooled onions, ground turkey, softened butter, seasonings, breadcrumbs, and egg. Process until well combined.

Shape the mixture into 1-inch meatballs and roll them lightly in flour, shaking off any excess.

In a large skillet, heat 1 tablespoon each of butter and vegetable oil over medium-high heat. Brown the meatballs in batches for about 5 minutes, then drain on paper towels.

Preheat the oven to 350°F. Place the browned meatballs on a baking sheet lined with aluminum foil and bake for 20 minutes until fully cooked.

In a large saucepan, combine the grape jelly and chili sauce. Heat over medium heat until the jelly has melted and the sauce is smooth.

Add the cooked meatballs to the sauce and simmer for 10-20 minutes, stirring occasionally to coat the meatballs evenly.

Serve the meatballs warm, garnished with fresh herbs if desired.