Clean and pat dry 4 pieces of fish fillets.
Prepare the green chutney by blending together 1 cup of fresh coriander leaves, 1/2 cup of fresh mint leaves, 4 green chillies, 1 tablespoon of grated coconut, 1 tablespoon of lemon juice, 1 teaspoon of cumin seeds, and salt to taste.
Spread the green chutney generously over each fish fillet, ensuring they are well coated.
Cut banana leaves into large squares and soften them by passing them over an open flame for a few seconds.
Place each marinated fish fillet in the center of a banana leaf square and fold the leaf to wrap the fish securely.
Secure the banana leaf parcels with kitchen twine or toothpicks.
Steam the wrapped fish parcels in a steamer for about 20-25 minutes, or until the fish is cooked through.
Carefully unwrap the banana leaves and serve the Patra Ni Machhi hot.