1. Make the blueberry jam. In a small bowl, whisk together the water and cornstarch. In a large skillet, add the blueberries, cornstarch mixture, sugar and cinnamon. Cook over medium-high heat, stirring constantly, until the jam is reduced and thickened. Remove from heat and allow to cool.

2. Make tangzhong. In a small saucepan, add bread flour and milk. Whisk constantly over medium heat until a paste forms. Remove from the heat and allow to cool for 10 minutes.

3. Make the dough. In the bowl of a stand mixer fitted with the dough hook attachment, add the warm milk, yeast, sugar, flour, tangzhong mixture, salt, egg and softened butter. Knead the dough on medium speed for 5 minutes. Transfer the dough to a greased bowl. Cover with plastic wrap.

4. Allow the dough to rise. Preheat the oven to 150F. Once the oven reaches this temperature, turn the oven off. Allow the dough to rise for 30 minutes.

5. Preheat oven to 350F. Line a baking sheet with parchment paper.

6. Divide and shape. Punch the dough down then transfer to a lightly floured surface. Divide the dough into 10 pieces. Working with one piece at a time, and covering the rest with plastic wrap, roll into a 9×4 inch rectangle. Cut 4 slits in the center of the dough, making sure to NOT cut through the ends. Spread a thin layer of the cooled blueberry jam over the rectangle. Roll the dough, starting at the short end, diagonally, into a log. Pinch the two ends together to seal. Place on a parchment paper lined baking sheet and repeat with the remaining dough.

7. Brush beaten egg over the dough, then bake in the preheated oven for 18-22 minutes, or until the rolls are golden brown in color. Enjoy!