Preheat the oven to 325 degrees F.

Heat the olive oil in a medium saute pan. Add the onions, thyme, salt, and pepper and cook over medium-low heat, stirring occasionally, for 8 to 10 minutes, until the onions are translucent but not brown. Off the heat, add the Worcestershire sauce, chicken stock, and tomato paste. Allow to cool slightly.

In a large bowl, combine the ground pork and ground beef, onion mixture, bread crumbs, and eggs, and mix lightly with a fork. Don't mash or the meat loaf will be dense. Shape the mixture into a rectangular loaf on a sheet pan covered with parchment paper. Spread the ketchup evenly over the top.

Bake for 1 to 1 ¼ hours, until the internal temperature is 160 degrees F and the meat loaf is cooked through. (A pan of hot water in the oven, under the meat loaf, will keep the top from cracking.) Serve hot.