Prepare the filling the day before or few days before and keep it in the fridge for up to one week or keep it frozen for up to one month
Prepare the water dough:
Combine flour, sugar, and salt. Whisk to combine. Add the oil and rub the flour mixture with the oil to form a coarse-crumb texture. Add water. I like to reserve some in case the dough might get too wet because different flour has different water absorption. Knead into a smooth dough. Cover and let it rest for at least 30 minutes. It is important to let the water dough rest so the dough can be smooth and stretchy later
Prepare the oil dough:
Combine the flour with oil. Knead into a soft dough. Round it up into a dough ball. Let it rest together with the water dough
Combine both doughs:
Give the water dough a few kneading just to smooth it out
Divide the water dough and oil dough into 12 pieces each. So you have a total of 24 pieces. Round them up into balls and cover tightly with a plastic wrap to prevent them from drying. Put them in an air-tight container is the best
Take one water dough and one oil dough. Flatten the water dough and then put the oil dough inside and wrap the water dough around it. Repeat with the rest of the dough. Remember to always keep them covered the whole time
Prepare the filling:
Portion the filling into 20-gram round balls. It's easier to wrap
Take one dough and keep the rest covered tightly. Roll it out into an oval shape, about 2 inches wide and about 4 inches long. Then roll it up like a Swiss roll. Do this to the rest of the dough
Then go back to the first one you roll and put it vertically and roll it out again into an oval and then roll it up into a Swiss roll again. If it's difficult to roll, rest it a bit longer and then try to roll it again. Repeat with the rest of the dough and keep them covered tightly. Rest them for 15 minutes
Wrap the filling with the dough:
Line a large baking sheet with parchment paper
Portion the red bean paste into 20-gram portion. Roll it into a round ball for easier wrapping
Take one dough and bring the two sides to the middle. Flatten with your palm and then roll it out into about 4-inch round.
Put one filling in the middle and gather the edge of the dough towards the center and pinch to seal tightly. Put the seam side down on the baking pan, about 1 inch apart. Flatten it slightly with your palm. Repeat with the rest of the dough and filling
Halfway through wrapping, start preheating the oven to 330 F (165 C) for a conventional oven, 310 F (155 C) for a convection oven.
Combine egg yolk with milk or water for the egg yolk wash. Brush the top of the pastry with an egg yolk wash
Baking:
Put the pan in the middle rack and bake for 15 minutes. After that take the baking pan out. Increase the oven temperature to 350 F (180 C) for a conventional oven, 330 F (165 C) for a convection oven. Let the pastry cool down for 5 minutes. Reapply the egg yolk wash and sprinkle with some white sesame seeds
Put the baking pan back into the oven and bake for 25 minutes or until the crust is nicely golden brown
Cool down:
Remove from the oven and let them cool down for 10 minutes on the pan. They are very soft when still warm. Then transfer to a cooling rack to let them cool down completely
How to store:
Let the pastry cool down completely and then store them in an air-tight container for about a week at room temperature
For longer storage, keep them in a freezer-friendly container and they can be kept frozen for up to one month
To serve, simply thaw at room temperature before serving. You can reheat it in the oven. Wrap it with an aluminum foil and bake at 350 F (180 C) for 4-5 minutes. Then let it cool down before consuming