Combine chicken, onion, 2 tablespoons cilantro, mint, oil, 1/2 teaspoon salt, 1/4 teaspoon pepper, 1/4 teaspoon cumin, Aleppo pepper, allspice and cinnamon in a large bowl. Cover and refrigerate for at least 10 minutes and up to overnight.
Position rack in upper third of oven; preheat broiler to high. Line a rimmed baking sheet with foil.
With damp hands, form about 3 tablespoons of the chicken mixture into an oval around a metal skewer. Add a second oval with another 3 tablespoons of the mixture on the same skewer. Repeat with the remaining chicken mixture to make 4 skewers with 2 kofta each. Place them on the prepared pan.
Broil the kofta, flipping once, until browned and an instant-read thermometer inserted in the center registers 165°F, 8 to 12 minutes.
Meanwhile, whisk yogurt, orange zest and juice in a small bowl with the remaining 2 tablespoons cilantro, 1/2 teaspoon salt and 1/4 teaspoon each pepper and coriander. Serve the sauce with the kofta.