1.  MAKE GLAZE Whisk all ingredients in saucepan until sugar dissolves. Reserve ¼ cup glaze mixture, then simmer remaining glaze over medium heat until slightly thickened, about 5 minutes. Cover and keep warm.

2. COOK VEGETABLES Line rimmed baking sheet with foil and coat lightly with cooking spray. Heat oil in nonstick skillet over medium heat until shimmering. Cook onion until golden, about 8 minutes. Add garlic and cook until fragrant, about 30 seconds. Transfer to large bowl.

3. PROCESS MEAT Process saltines and milk in food processor until smooth. Add beef and pork and pulse until well combined, about ten 1-second pulses. Transfer meat mixture to bowl with cooled onion mixture. Add eggs and yolk, mustard, Worcestershire, thyme, parsley, 1 teaspoon salt, and ¾ teaspoon pepper to bowl and mix with hands until combined.

4. BROIL Adjust oven racks to upper (about 4 inches away from broiler element) and middle positions and heat broiler. Transfer meat mixture to prepared baking sheet and shape into 9- by 5-inch loaf. Broil on upper rack until well browned, about 5 minutes. Brush 2 tablespoons uncooked glaze over top and sides of loaf and then return to oven and broil until glaze begins to brown, about 2 minutes.

5. BAKE Transfer meatloaf to middle rack and brush with remaining uncooked glaze. Reduce oven temperature to 350 degrees and bake until meat loaf registers 160 degrees, 40 to 45 minutes. Transfer to carving board, tent with foil, and let rest 20 minutes. Slice and serve, passing cooked glaze at table.