Heat oven to 400°F. Lightly coat a 9-by-3-inch loaf pan with cooking spray and set aside.
In a large bowl, whisk together the eggs, mustard, oil, salt, pepper, and 1 tablespoon of the tomato paste. In a food processor, chop the garlic, onion, and carrot until finely chopped. Transfer to the bowl. Finely chop 2 chicken-breast halves (about 1/8-inch dice), and cut 1 chicken-breast half into 1/2-inch pieces. Add to the bowl along with the scallions, apple, and bread crumbs. Using your hands, mix to combine well.
Place half the meat-loaf mixture in the pan. Sprinkle on the pistachios in 1 layer. Top with the remaining meat-loaf mixture, pressing gently. Bake for 20 minutes.
Meanwhile, whisk together the maple syrup and remaining tomato paste. Brush the glaze over the meat loaf and return it to the oven for 10 minutes. Remove and let rest, covered with foil, for 10 minutes before serving.