Rinse banana leaves well and wipe down to dry and rid off any dirt or debris. Cut into about 6-inch squares.
Peel, devein, and cut shrimp into small pieces. Reserve shrimp heads.
In a bowl, combine ¼ cup water and shrimp heads. With the back of a spoon, gently press heads to extract the juice. Using a fine-mesh sieve, strain and set aside juice.
In a bowl, combine shrimp, pork, shredded young coconut, onions, garlic, and shrimp juice. Season with salt and pepper to taste.
On a banana leaf, spoon about 3 tablespoons of shrimp mixture. Fold sides of the leaf over filling to form a packet and tie with kitchen twine to fully secure.
In a wide pan, arrange banana packets in a single layer and pour coconut cream.
Cook over medium heat for about 15 to 20 minutes. Transfer banana packets onto a serving platter and keep warm.
Simmer coconut sauce in the pan until slightly reduced and thickened. Serve in a bowl on the side to spoon on the pinais.