Japanese bread/Dinner Rolls are pillowy soft thanks to a simple technique involving a roux known as tangzhong. The roux is mixed into the dough, producing a tender bread each and every time.
Combine all of the ingredients in a small saucepan, and whisk until no lumps remain.
Place the saucepan over low heat, and cook the mixture, whisking constantly, until thick and the whisk leaves lines on the bottom of the pan, about 3 to 5 minutes.
Transfer the tangzhong to a small mixing bowl or measuring cup and let it cool to room temperature.
Combine the tangzhong with the remaining dough ingredients, then mix and knead using a stand mixer, for 6 to 8 minutes until a smooth, elastic dough forms.
Shape the dough into a ball, and let it rest in a lightly greased covered bowl for 60 to 90 minutes, until puffy but not necessarily doubled in bulk.
Gently deflate the dough, divide it into 8 equal pieces, and shape each piece into a ball.
Preheat the oven to 350°F. Brush the rolls with milk or egg wash (1 large egg beaten with 1 tablespoon cold water), and bake for 25 to 30 minutes, until golden brown on top; a digital thermometer inserted into the center of the middle roll should read at least 190°F.
Remove the rolls from the oven. Allow them to cool in the pan for 10 minutes, then transfer them to a rack to cool completely.