Soften the gelatin in the water and let sit for 5 minutes in a dutch oven. Heat the gelatin over medium high heat until fully melted. Add the sherry, soy sauce, scallions, ginger, garlic, molasses, hoisin sauce, 5-spice powder, pepper flakes. Stir.
Place the beef into the pot and bring to simmer. Cover the pot with foil and then the lid. Place in 300 degree oven for 2-2-1/2 hours stirring once midway. Remove from the oven.
With a slotted spoon remove the meat from the liquid. Strain the liquid and put in a fat seperator. Pour the defatted liquid back into the pot. On mediuam high simmer the sauce until thickened (approx 20 minutes). To the reduced liquid add 1 teaspoon of corn starch dissolved in 1 Tablespoon of water. Cook for several minutes. Break the meat into 1-1/2 inch pieces and add back into the pot. Cover and take off the heat to allow the meat to warm back up.
Serve with white rice with sliced green onions. Broccoli or Bok choy are good sides.