Add the glutinous rice flour into a cold pan and heat over medium heat. Stir and cook the flour until the color turns off-white and you can smell some nuttiness coming from the flour, 5 minutes or so.

Add the shredded coconut and sesame seeds into a grinder or using a mortar and pestle, coarsely grind both.

Peel the winter melon by removing the tough skin by 1/4” (4mm) using a knife, until no green skin is visible on the flesh. Remove the seeds using a knife by cutting off the soft part between the seeds and the flesh. Chop the melon into 1” (2.5 cm) pieces to yield slightly over 150g, then puree in a blender until smooth.

Weigh 150g of the purée into a medium saucepan and add the 36 g water, 30 g coconut oil, 75 g sugar, and 1/4 teaspoon salt. Bring to a simmer over medium heat, stirring frequently, about 5 minutes, or until slightly thickened.

Add the shredded coconut and sesame seed mixture and ground ginger, and continue to cook until most of the liquid has evaporated.

Turn to low heat. Add in toasted glutinous rice flour in several rounds, stirring very thoroughly by scraping the pan between additions. Cook and stir for another 1 to 2 minutes until the mixture is very thick and translucent. Transfer to a bowl, cover with plastic wrap pressed directly on the surface to prevent skin from forming, let cool completely.

Once cool, divide filling into 8 equal portions, rolling paste into balls. Cover and set aside.

Sift the 90 g all-purpose flour, powdered sugar, and salt into the bowl of a stand mixer. Add the butter and ice water. Mix with a spatula until a rough dough forms. Place the bowl in the mixer with the dough hook attachment. Drape a piece of the dough over the hook. Turn the mixer to setting 4 and knead until smooth and elastic, about 10 minutes. Depending on the size of your mixer, it may be necessary to stop the kneading occasionally and lift the dough over the hook (*Footnote 1). You can also hand knead the dough. To test the dough, stretch it into a thin semi transparent sheet and it should hold well. Knead a bit longer, if needed. Once done, cover the dough and rest for 10 minutes.

Combine the 110 g cake flour and shortening in a medium-sized bowl. Mix and press it together using your hands, until the dough forms. Further shape and knead it on a working surface until uniform and smooth. Cover and rest for 5 minutes.

Divide the water dough into 8 even pieces. Work on one dough at a time, use your hands to pull the dough towards the center, until it forms a ball. Pinch to seal the end and set aside. Always cover the dough with plastic wrap.

Divide the oil dough into 8 even pieces. Form each piece into a dough ball using your hands, covering them as you go.

Flatten a ball of water dough with your palm and spread it with your fingers so that the center is thicker than the edges, about 3 1/4” (8 cm) wide. Place a ball of oil dough in the center. Lift the edges of the water dough over the oil dough to wrap it and pinch at the top to seal it. Shape the ball to smooth it out. Set it aside and cover it. Repeat with all pieces of dough.

Preheat the oven to 350°F (176°C).

Take a formed ball, sealed-side down, and flatten it with your palm. Gently roll it into a 5” (12.5 cm) long strip. Flip it over so it’s seam-side up. Starting from the short side, roll it into a thick jelly roll. Turn the roll 90° and flatten it with your hand. Again roll it into a 5”(12.5 cm) strip and then into a jelly roll. Cover and set aside. Repeat with the remaining balls.

Beginning with the first roll you made, take a roll and press into the middle so the swirled ends are pressed out. Then fold the swirled ends into the center and press them down so that a flat disc is formed. Roll this disc out so that it is 4” (10 cm) in diameter. Place the filling in the center. Lift and stretch the dough over the paste ball to cover completely, and pinch to seal. Roll between your palms to smooth it out. Flatten gently with your palm. Then roll into a flat disk that is about 3 1/4” (8 cm) in diameter. Repeat with all the dough and cover all the dough pieces with plastic wrap as you do so. (*Footnote 5)

Line a baking tray with parchment paper. Place the pastries on it, at least 1” (2.5) apart. Gently slice two slits on the top.

Lightly beat the yolk. Brush a thin layer of the egg wash onto the tops of the pastries. Wait 5 minutes and brush with a second layer of yolk.

Wet your fingertip with water and dip it into the sesame seeds so the seeds stick to your finger. Tap the top of each pastry to decorate.

Bake at 350°F (176°C) for 15 to 20 minutes, until the egg wash turns golden and the pastries are cooked through and flaky. Once done, remove the baking sheet from the oven and let cool for 15 minutes before serving.

After completely cooling, you can store the baked cakes in an airtight container at room temperature for up to 2 days, in the fridge for up to 2 weeks, or in the freezer for 3 months.