In a small bowl, combine tomato paste, soy sauce, brown sugar, garlic, red pepper flakes, ginger and half of sesame seeds. Blitz with an immersion blender or add to blender and blitz until smooth. Pour sauce over chicken and toss to coat. Cover with lid and cook for 6 hours.
Preheat oven to broil. Place a baking rack on a parchment paper covered baking sheet. Line out chicken wings on rack. Place under broiler for 3 minutes on each side. Serve with a sprinkle of scallions and remaing sesame seeds.