Preheat the oven to 400F.
Melt the butter in a pan set over medium heat.
Add the onions and celery, a pinch of salt, and cracked black pepper. Cook for 6-8 minutes, or until slightly softened. Set aside to cool.
Make a panade by mixing together breadcrumbs and milk and let sit until the breadcrumbs soak up the liquid.
In a large bowl, add the turkey, cooled vegetables, spices, remaining salt, and herbs.
Add the panade, parmesan cheese, eggs, and oil.
Mix the meatballs together until just combined. Overmixing will make the meatballs tough.
Using a 1 ½ tablespoon size scoop for small meatballs (or a 3 tbsp scoop for large ones), scoop and roll them into meatballs and distribute them onto two baking sheets lined with parchment. Tip: spray the scoop and your hands with non-stick spray to keep the mixture from sticking.
Bake for 12-15 minutes, then swap the trays and flip each meatball over.
Bake for another 10 minutes until slightly golden and the internal temperature measures 165F with an instant read thermometer.
Serve with your favorite gravy and mashed potatoes.