Preheat the oven to 350℉. Line a large rimmed baking sheet or jelly roll pan with parchment paper and set aside.
Heat 2 tablespoons of oil in a large skillet over medium heat. Add the diced onion with a pinch of salt and cook until soft and translucent. Stir in 4 cloves of minced garlic and cook for about 1 minute.
Add 12 ounces of finely chopped mushrooms, about 4 teaspoons of freshly minced herbs, and 1 small diced apple. Cook, stirring often, until the mushrooms release their liquid and most of it has evaporated, about 6 to 8 minutes. Stir in 2-3 tablespoons of Worcestershire sauce, 1½ teaspoons tomato paste, and 3 tablespoons chicken broth (or water), then remove from the heat.
Spread the mixture on a plate or lined baking sheet and let it cool completely.
In a large mixing bowl, combine 2 pounds of ground turkey, 1⅓ cups breadcrumbs, 2 eggs, a pinch of salt and black pepper. Gently mix with your hands until partially combined.
Add the cooled vegetable mixture to the bowl and mix again until everything is evenly distributed, being careful not to overwork the meat.
Transfer the turkey mixture to the prepared baking sheet and shape it into a loaf with your hands.
In a small bowl, whisk together ⅓ cup ketchup, 2 teaspoons Dijon mustard, 2 tablespoons brown sugar, and 2 teaspoons of red wine vinegar. Brush about half of this glaze over the top and sides of the loaf with a pastry brush. Reserve the remaining glaze for later.
Cover the meatloaf loosely with foil and bake for 35-40 minutes.
Remove the foil, increase the oven temperature to 400℉, and brush the loaf with the remaining glaze. Bake for an additional 10-15 minutes, or until the internal temperature reaches 160 degrees F in the center.
Let the meatloaf rest for 5-10 minutes before slicing and serving.