I bought this jar of chestnuts in sugar syrup at a 100 yen shop. It contains 145 g, of which 75 g is solid. There were 10 chestnuts, so I chopped up 4 to mix into the sweet potato paste, and used the rest whole, one per bun.
Make the sweet potato paste filling. Put the mashed sweet potatoes and the chestnuts in syrup in a pan (add the syrup) and simmer to reduce. Add sugar if you like.
Prepare the bread dough. Put all the ingredients from the flour to the salt in the ingredient list in a bowl (keep the salt and yeast apart in the bowl). Warm the milk in the microwave, and pour over the yeast. Start mixing and kneading the dough.
Add the butter halfway through and knead it in. Round the dough off into a smooth ball, cover with a tightly wrung out moistened kitchen towel and plastic wrap, and leave for the 1st rising until doubled in volume.
Punch down the dough and divide it. I divided it into 6 portions this time. Cover the dough with a moist kitchen towel again and rest for 15 minutes.
Deflate the dough again, and form into buns with the paste filling. I made round buns first and then kind of made them into chestnut shapes. Place the buns with the seam sides down on a baking sheet lined with parchment paper.
Cover again with the moistened kitchen towel and plastic wrap, and leave for the 2nd rising. It's done when it has doubled in volume. Pinch the pointy ends to make the buns more chestnut shaped.
Brush the buns with the remaining egg, and sprinkle on the white poppy seeds. Bake at 180°C for about 13 minutes and they're done!
The buns are about this size.
They look like this in the middle. I used 45 g of paste filling per bun and had some left over, so if you stuff the buns a bit more you should be able to use it all up.
I these are made with dark brown sugar (20 g) instead of light brown sugar. The buns became a little bit darker.
This one is stuffed half and half with Recipe ID: 1239763 Chestnut paste and chunky red bean paste.
Story Behind this Recipe
I got the inspiration to make this while I was at work.
You can use black cocoa or instant coffee (4 g if using instant coffee) instead of cocoa powder. If you don't have any roasted wheat germ, substitute whole wheat flour. The paste filling is not that sweet. Adjust the sweetness to taste.