Set an oven rack in the middle of the oven and preheat to 350°F Set a rack in a rimmed baking sheet. Fold a piece of heavy duty aluminum foil to form a rectangle 6 1/2 by 3 1/2 inches. Set the foil on the rack and spray it with oil spray. Poke holes in the foil at 1/2" intervals.
Melt butter in a skillet over medium heat. Add onion and mushroom and cook until starting to brown, 10-12 minutes. Add tomato paste and cook, stirring constantly, until browned, 3 minutes. Reduce heat to low. Add 2 T chicken broth and garlic. Scrape any stuck-on brown bits from the bottom of the pan with a wooden spoon/spatula, and cook until thickened, about 1 minute. Transfer to a large bowl and set aside to cool.
Whisk eggs with soy sauce and 6 T chicken broth. Sprinkle gelatin over surface and set aside until gelatin softens, about 5 minutes.
Pulse bread in food processor until finely ground, 5-10 pulses. Add gelatin, mushroom mixture, parsley, basil, oregano, mustard, pepper and thyme to processor and pulse until mushrooms are finely ground, about 10 1-second pulses. Transfer mixture back to bowl. Add turkey and mix with hands until combined.
Shape mixture into a loaf about 6 1/2 by 3 1/2 inches and lay on foil rectangle. Bake in preheated oven until interior temperature is 155-160F, 75-90 minutes. Remove from oven and turn on broiler.
While meatloaf is cooking, combine all glaze ingredients in a small pot. Bring to a simmer over medium heat. Cook, stirring occasionally, until thick and syrupy, about 5 minutes.
Spread half of glaze evenly over meatloaf. Place under broiler until glaze bubbles and browns at edges, 2 minutes. Spread remaining glaze evenly over meatloaf and return to broiler until glaze again bubbles and begins to brown, about 2 minutes. Tent with foil and let stand at room temperature for 20 minutes before slicing and serving.