Heat oil and ghee in a heavy bottomed vessel, add few curry leaves, cloves, cinnamon, cardamom, pepper corns and saute for few secs till the aroma emanates the kitchen. Add garlic slices and saute for for few secs. Add ginger paste and saute for few secs. Add the green chillis and sliced onions and fry for 4 mts.
Add turmeric pwd and combine. Add the chicken pieces and cook over medium heat for 7-8 mts.
Add the thin coconut milk and salt and combine. Cook without lid for 5-6 mts. Add garam masala pwd, fennel pwd and potato cubes and place lid. Simmer till the chicken and potatoes turn tender and the gravy thickens. Turn off heat. Add the thick coconut milk, few fresh curry leaves, lemon juice and pepper pwd and combine.
Serve warm with appam, rice or roti.