Rinse and pat dry the duck, removing any innards in the cavity.

Generously sprinkle the entire duck body with salt, including the body cavity. Set aside.

In a small pan, roast coriander and peppercorns over medium heat until fragrant—2 minutes.

Combine shallots, galangal, ginger, garlic, turmeric, lime, salt, kaffir leaf, shrimp paste, serrano chili, sesame oil, water, sugar, and lemongrass into a food processor or blender, including the toasted pepper and coriander. Pulse until a loose paste forms; okay to have a few large pieces of ingredients. To loosen paste, add small amounts of water and scrape the sides if needed. Set aside.

Over an open flame (on a gas stovetop or barbecue), prepare your banana leaf. Carefully place a portion of the banana leaf on top of the flame. When the leaf becomes fragrant, continue passing the remainder of the leaf over the flame until the whole leaf is fragrant and gently toasted.

Lay out a long piece of foil and place the banana leaf on top; both should be horizontal. The whole leaf will not fit and some will be hanging off the edge.

Move the duck to the banana leaf and smother one side with a generous portion of paste. Place the duck lengthwise and paste side down onto the center of the banana leaf, leaving about 1 foot of leaf to wrap around (wrapping the duck is similar to wrapping ingredients into a burrito). Spread the remaining paste onto the duck and begin to wrap the duck—fold the 1 foot of banana leaf over the duck and roll until the duck is wrapped in the leaf. Note, the banana leaf will not cover rear and the head.

Fold the foil over the duck and tuck in the edges. Repeat this step with three more layers of foil, making sure the duck is sealed.

Preheat grill to 350 degrees, the place duck in the center. Roast for 3 hours, or until the internal temperature reads 175 degrees on the thicker part of the leg.

Carve or shred the duck with a fork and serve hot with cooked juices and paste, with rice, cucumber, or tomato.