Soak the goji berries in water, rinse to remove any dust, then drain. Rinse the osmanthus flowers briefly to clean, then steep them in a cup with 3/4 cup hot water (about 200 ml) to make an infusion. Pour the water into a pot and bring to a boil. Add the rock sugar and stir until dissolved. Taste and adjust the sweetness as desired.

Once the sugar has dissolved, mix the gelatin powder and agar powder together, then gradually add to the pot, stirring constantly until completely dissolved. Skim off any foam. Pour in the osmanthus infusion, then add the goji berries. Stir for a few seconds, then turn off the heat.

Pour the mixture into a large mold or small molds as you like. Let cool slightly, then refrigerate until set. Once firm, remove from the mold and cut into squares for serving.