Heat oven to 375 degrees. Cut the bread into 1 inch cubes and place in a small bowl. Pour the milk over the bread. Set aside for five minutes.
Heat the olive oil in large skillet over medium heat. Add onion, celery, and garlic. Cook until soft and translucent, about 3-5 minutes. Remove from heat. Let cool for five minutes.
Place carrots in a large mixing bowl. Add the milk and bread mixture, ground sirloin, ground pork, eggs, parsley, Dijon mustard, salt, and pepper. Add onion mixture. Combine well using your hands or a rubber scraper.
Place mixture in a large ungreased baking dish or roasting pan. Shape into a 5 by 12 inch loaf. Overlap bacon slices across the top, covering the meat. Place potatoes and leeks around the loaf. Season with salt and pepper as needed.
In a small bowl, combine the brown sugar, ground mustard, and 2 tablespoons of water. Stie in tomato paste making a glaze. Brush the meat loaf all over with the glaze.
Bake, brushing every fifteen minutes with glaze until juices run clear when loaf is pierced with a two-pronged fork and bacon is crisp, 1 to 1 and 1/4 hours. Let cool 10 minutes before slicing. Serve with potatoes and leeks on the side.