1. Ingredients: 125 grams of frozen sea vegetables (gelidium), 25 grams of white vinegar, and 15 kilograms of water.

2. Method: Place the frozen sea vegetables on a board and tap gently with a rolling pin to remove the sediment. Soak the beaten frozen vegetables in water for 20 minutes to soften them, take them out and rinse them thoroughly, so that some sediment can be removed.

3. According to the ratio of half a kilogram of frozen vegetables to 30-40 kilograms (125 grams plus 15-20 kilograms) of water, put the pressure cooker on for 15 minutes.

4. Then cook on low heat for 2-3 hours. After simmering the frozen vegetables for 3 hours, use gauze or a leaky mesh filter pot for filtering soy milk to simmer all the slurry.

5. Add water to the pot again. The amount of water is enough to cover the frozen vegetables. Continue to cook on medium-low heat for 15 minutes. Filter all the slurry in the pot again.

6. For the third time, add enough boiling water to the pot to cover the frozen vegetables, continue to cook over medium-low heat for 20 minutes, and filter the slurry for the third time. The slurry filtered three times should be put in the same container. When cooking the last time, pay attention to the heat preservation of the first two times. Add white vinegar, stir evenly and let it cool.