1. Wash the white kidney beans, put them in an electric pressure cooker, add twice as much water, and select the beans
2. Peel the grapefruit and squeeze the grapefruit juice; put the cooked white kidney beans into a food processor to make bean paste
3. Put the bean puree and grapefruit juice into the pot together, add an appropriate amount of rock sugar, heat on medium heat first, turn to low heat when it thickens, and keep stirring until the water is dry and ready for grapefruit filling.
4. Mix and knead all the ingredients of the water and oil skin dough (150 grams of ordinary flour, 60 grams of butter, 25 grams of caster sugar, 42 grams of water) to form a smooth dough
5. Mix all the ingredients of the pastry dough (100 grams of plain flour, 50 grams of butter) and knead it into a dough
6. Divide the water and oil skin dough and the pastry dough into 9 equal parts, and let them rest for about 15 minutes; take a small water and oil skin dough and squeeze it on the palm of your hand.
7. Put the small pastry dough on the flattened water and oil-crust dough; wrap the pastry dough with the water-crusted dough
8. Place the wrapped dough on the cutting board with the mouth facing up, and flatten it with the palm of your hand; use a rolling pin to roll the dough into an oval shape; roll the rolled dough sheet from right to left
9. Roll the rolled dough into an oval dough sheet again with a rolling pin; roll it up again from top to bottom; roll the rolled dough into a round dough sheet with a rolling pin
10. Wrap the grapefruit filling; seal the mouth with the mouth facing down; hold the dough with your hands and gently flatten it. Put it on a baking tray lined with tin foil and bake in the oven