Boil cassava peel until tender and soak in cold water for a while, drain and cut to taste.
Saute onion, garlic, cayenne pepper and galangal until fragrant.
Add cassava peel, oyster sauce, sugar and salt. Stir well and cook until flavors mingle.
Shortly before finishing, add the leeks and stir well. Serve with salted fish fried to accompany warm rice.