For the broth, place chicken, mushrooms, green onions, ginger, and bay leaves in a cheesecloth or fine-mesh bag. Submerge in a pot of water and simmer over medium heat for 45 minutes. Remove the bag. Reserve 1⅔ cups/400 milliliters of broth, stir in gelatin until fully dissolved, and pour into a shallow dish. Cover and chill for at least 3 hours until set.

For the dough, mix flour and salt. Add boiling water and stir for 2 minutes until coarse crumbs form. Add cold water, then knead on a floured surface for 5–6 minutes until smooth and elastic. Cover and refrigerate until ready to use.

For the filling, combine ground beef, green onions, shallot, ginger, and soy sauce in a bowl. Cut chilled broth into small cubes and fold into the beef mixture until evenly combined.

Divide the dough into small pieces. Roll each piece into a circle, place filling in the center, moisten edges, and fold edges to the center to seal. Place each dumpling on parchment paper.

Steam the dumplings in a steamer over medium heat for 10 minutes.

Whisk together all sauce ingredients until combined. Serve the dumplings with sauce, garnished with green onions and sesame seeds.