Place olive oil in a skillet over medium heat. When hot, add onion and sauté until softened, 8 to 10 minutes. Add garlic and cook for 1 minute. Stir in barbecue sauce and Worcestershire sauce, remove from heat, and cool.

Preheat oven to 375ºF with a rack placed in the middle position.

Mix together breadcrumbs, cooled onion mixture, parsley, granulated onion, and enough half & half to make a thick paste; stir in eggs. Crumble ground beef onto a clean work surface; crumble pork on top of beef, distributing evenly. Sprinkle sliced green onions over meat mixture, spread breadcrumb mixture evenly over meat, then sprinkle with Parmesan cheese and salt, pepper, and cayenne to taste. Using your hands, mix gently; divide into 2 equal portions and shape into loaves.

Line a sheet pan with foil and add a baking rack. Transfer meatloaves to rack, place in the oven, and roast for 30 minutes. Mix remaining ½ cup of barbecue sauce with catsup. Baste meatloaves with about half the mixture and rotate the pan. Continue to roast until meatloaves are browned and an instant-read thermometer reaches 145ºF in the center of the meatloaves, 30 to 45 minutes. Remove from the oven, baste with remaining barbecue mixture, and allow meatloaves to rest for 5 minutes. Cut into thick slices and serve.