Heat 2 tbsp oil in large Dutch oven on medium-high.  Add onion and cook, stirring occasionally, until it begins to change color.  Reduce heat to medium and cook, stirring occasionally, until tender, 3 to 4 minutes more.  Stir in garlic and chile and cook 1 minute.  Stir in ginger, garam masala, coriander, paprika and ½ tsp salt and cook, stirring, 2 minutes.  Stir in tomato paste and cook 2 minutes. Season chicken with ½ tsp each salt and pepper, then add to pot and cook, tossing occasionally, until no longer pink, 5 minutes.  Stir in chicken broth and gently simmer, covered, until chicken is cooked through, 6 to 8 minutes.  Stir in yogurt and serve over rice, sprinkled with cilantro if desired.