Heat oil in a heavy-bottomed pan over medium heat.
Sauté chopped onion until golden brown and translucent.
Add ginger garlic paste and cook for 1-2 minutes until fragrant.
Add tomatoes, fennel seeds, cinnamon, and crushed peppercorns. Cook until tomatoes break down completely.
Add chicken pieces and mix well to coat with the spice mixture.
Pour in water and add curry leaves. Season with salt.
Bring to a boil, then reduce heat and simmer covered for 15-20 minutes until chicken is cooked through.
Adjust consistency by adding more water if needed or cooking uncovered to thicken.
Garnish with fresh curry leaves and serve hot.