In a bowl, mix yogurt, tomato paste, red pepper paste (if using), and all the dry spices.
Add lemon juice and mix until well combined.
Score the chicken drumsticks for better absorption of flavors.
Peel and cut the potatoes into large cubes.
Coat both the chicken and potatoes thoroughly with the marinade.
Cover and let it rest for at least 1 hour (overnight for best results).
Heat ghee or oil in a large, deep pan over medium-high heat.
Add the marinated chicken and potatoes, searing them for 7-8 minutes on each side until golden brown.
Pour in chicken stock, cover, and let it cook for 10-15 minutes on low heat.
Remove the lid and cook on medium-high heat for another 5-10 minutes until the liquid reduces into a thick, flavorful gravy.
Sprinkle garam masala and chopped coriander on top.
Serve hot with rice, naan, or flatbread for a complete meal.