Start by cleaning your tilapia thoroughly. Remove all scales, innards, and gills, then rinse under cold water and pat dry with paper towels. Season the fish inside and out with salt and pepper.
Mix together the chopped tomatoes, shallots, and ginger in a bowl. Add the tamarind powder and stir until well combined.
Fill each fish cavity with the tomato mixture, being careful not to overstuff.
Wash your pechay leaves and pat them completely dry. Lay out 2-3 leaves slightly overlapping each other.
Place a stuffed fish in the center of the pechay leaves. Wrap the leaves around the fish, then tie securely with pandan leaves or kitchen twine. Repeat with the second fish.
Place your wrapped fish parcels in a large pan. Pour in the coconut milk and add the finger chilies. Season with a little more salt and pepper.
Cover the pan and bring to a gentle simmer over low heat. Never let it boil rapidly - you want just tiny bubbles breaking the surface. Cook for 20-25 minutes.
You'll know the fish is done when the flesh turns opaque and flakes easily when tested with a fork.
Let rest for 5 minutes before serving. Place on a serving platter and pour the creamy coconut sauce over the top. Serve hot with steamed rice.
Remember: Keep the heat low and steady throughout cooking to prevent the coconut milk from curdling. The gentler you cook it, the creamier your sauce will be.