Preheat your oven to 350°F (175°C). Line a rimmed baking sheet with parchment paper or aluminum foil. If you have a wire rack, place it on the baking sheet—this allows fat to drip away and gives you a nice crust on the bottom.
Create the panade: In a small bowl, combine the breadcrumbs and milk. Stir and let sit for 5-10 minutes until the breadcrumbs have absorbed all the liquid and formed a thick paste. This is the secret to moist meatloaf.
In a small skillet over medium heat, add 1 tablespoon of olive oil. Sauté the minced onion for 4-5 minutes until translucent. Add the garlic and cook for 1 more minute. Set aside to cool completely. (Hot onions will cook the eggs prematurely!)
Make the glaze: In a separate small bowl, whisk together all glaze ingredients. Set aside half of the glaze for basting during cooking, and reserve the other half for serving.
Combine the meat mixture: In a LARGE bowl, combine all three ground meats, the cooled onion-garlic mixture, the panade, beaten eggs, parsley, Worcestershire sauce, Dijon mustard, salt, pepper, thyme, and the gelatin-broth mixture. Use your hands to mix gently until just combined—about 30-45 seconds. Do not overmix!
Shape the loaf: Transfer the meat mixture to your prepared baking sheet. Shape into a loaf approximately 9x5 inches, making the ends slightly higher than the middle to prevent burning.
Apply the first glaze: Brush about ⅓ of the glaze evenly over the top and sides of the loaf.
Bake for 45 minutes at 350°F.
Remove from oven and brush with another ⅓ of the glaze. Return to oven for 15 more minutes, until internal temperature reaches 160°F (71°C).
Remove from oven, brush with remaining glaze, and LET REST FOR 10-15 MINUTES. This is non-negotiable for juicy meatloaf.
Slice into 1-inch thick pieces and serve with mashed potatoes and green beans. Drizzle with reserved glaze.