In a large mixing bowl, combine ground turkey, breadcrumbs, grated Parmesan cheese, egg, minced garlic, dried oregano, salt, and black pepper. Mix until uniformly blended.

Roll the mixture into 1-inch meatballs and place on a plate, leaving space between.

Heat olive oil in a large skillet over medium heat. Add the meatballs in batches and cook until browned and cooked through, about 5-7 minutes. Transfer to a plate.

In the same skillet, melt butter and sauté the chopped onion for 3-4 minutes until soft. Add minced garlic and sauté for another minute.

Stir in pumpkin puree, chicken broth, and heavy cream. Bring to a gentle simmer for about 5 minutes.

Season the sauce with chopped sage, nutmeg, and salt and black pepper to taste. Stir well.

Return the meatballs to the skillet, ensuring they are submerged in the sauce. Cover and let simmer for 10-15 minutes.

Serve the turkey meatballs hot, drizzled with the creamy pumpkin sage sauce.