Prepare the dough. In a bowl, mix all the ingredients except for the butter.
With a rubber spatula, mix the dry ingredients with the liquid. Once it comes together, transfer onto a working surface and knead with your hand. Rub in the butter and knead well.
When the dough has been worked to enough to activate the gluten, tear off 1/3 of the dough and form round shape with the remaining 2/3.
Rub in the matcha paste to the 1/3 dough and knead well until you get an even green color. Together with the dough from Step 3, let the dough rise for the first proof for 40 - 60 minutes.
Cut the sweet potatoes into 8 mm cubes and microwave or steam to soften. I used homemade boiled adzuki beans, but store-bought is also OK.
When each portion of dough has doubled in size, punch down the dough and form into a ball. Cover the dough with a damp cloth and rest for 20 minutes.
Roll out the white dough into the size of the loaf pan.
On top of the dough, line up the sweet potatoes cubes.
Then cover it with matcha dough, which was rolled out slightly smaller than the white dough. Make sure you press the air out of the dough in between the potatoes.
Scatter the boiled adzuki beans evenly, but make sure adzuki won't fall out when you roll the dough.
Roll it up from the front. Make sure there is no air pockets trapped inside by rolling the dough tightly. Seal the seams firmly.
Put the dough into a lightly buttered loaf pan. Cover it with a damp cloth and rise for the second time for 40 - 60 minutes.
When the dough has risen to 80-90% of the pan, close the lid (if you are using a round loaf pan, rise until the dough gets to 80 - 90% of the closed pan).
Bake for 20 minutes in a preheated oven at 200℃ then lower to 180℃ and bake for 10 minutes. After it has baked, take out bread immediately from the pan and cool on a rack.
Slice after it's completely cooled. If you scatter the sweet potatoes and adzuki beans evenly, right to the edges of the dough, it will look delicious and pretty all the way to the ends.
Story Behind this Recipe
I wanted to bake a "Japanese" bread.
By separating the kneaded dough into two and mixing one with dissolved matcha, it makes the process easier and you can get a nicely kneaded dough. Scatter sweet potatoes and adzuki beans evenly all the way to the edges. Make sure no air gets in when rolling the dough.