In a stand mixer fitted with the paddle attachment, combine the flour, sugar, salt, and yeast. Make a well in the center of the mixture and place one of the eggs, milk, and tangzhong in it. Switch to the dough hook attachment and, on medium speed, knead the ingredients until a dough forms. Add the butter and continue kneading for 18 to 20 minutes, or until the dough is smooth and elastic. You should be able to stretch a piece of the dough very thin without it tearing.

Coat the inside of a large bowl with oil. Form the dough into a ball shape and place it in the bowl and cover it with a wet towel for 40 minutes or until it has doubled in size.

Deflate and divide the dough into six equal pieces and form each into a ball. Cover the dough balls with plastic wrap and let them rest for 15 minutes.

Roll each dough ball into an oval shape. Sprinkle a handful of raisins across the dough and, using your rolling pin, press the raisins into the dough. Take one end of the dough and fold to meet the middle of the oval. Take the other end and fold to meet on top. Turn the dough over, so that the folds face down and roll and flatten dough with the rolling pin. Flip dough again, so folded side faces up. Roll the dough up from top to bottom.  Knead into a ball shape. Repeat this step of rolling and wrapping fillings with the rest of the dough balls.

Place the dough balls seam side down in a prepared 8-inch springform baking pan leaving the space in the center clear. Cover the pan with plastic wrap or a wet towel for 45 to 60 minutes, or until the rolls have doubled in size.

Preheat the oven to 350°F. Beat the other egg in a small bowl and brush it on top of the rolls. Bake the rolls for 30 to 35 minutes or until they are golden brown. Cool completely on a wire rack.