Spray nonstick oil onto the baking sheet and set aside until ready to use.
Cut the mozzarella cheese bar into cubes and set aside until ready to use.
Attach your hook attachment to the electric mixer. Place the flour, white granulated sugar, and salt. egg, yeast mixture, and Tangzhong mixture in the electric mixing bowl. Mix the ingredients to low speed until the mixture will look like wet sand.
Now you can add the softened butter. Mix to medium speed. The mixture will look really wet, but eventually, it will form into a dough. Mix until the flour is smooth, about seven minutes of mixing.
Remove the dough and form it into a ball. Brush the bowl you used with oil and return the dough back into it. Turn the dough so that it will be coated with oil. Cover and place the dough in a warm place for one hourPro tip: What I do is turn my oven to its lowest setting for fifteen minutes and turn it off. This will be the warm place I use for proofing. After an hour, sprinkle your working area with flour, and put your dough there. First form the dough into a ball and divide it into two. Cut the dough into small pieces, to make thirty-five small balls. You can also weigh the dough. The size should be a little bigger than that of a pingpong ball.
Flatten the dough and fill it with cubed mozzarella cheese. Seal the dough and put it into the prepared baking sheet forming them to look like a Christmas tree.
Cover the dough with a cloth and let the dough sit in a warm place for another thirty-five minutes.