Prepare the Tangzhong:

• In a small saucepan over low heat, whisk together water, milk, and bread flour.
• Stir continuously until it thickens into a paste (about 2 minutes).
• Remove from heat, cover, and let cool to room temperature.

Make the Dough:

• In a large bowl, combine bread flour, sugar, and salt.
• Add yeast and mix well.
• Stir in melted butter, milk, Tangzhong, and egg until a shaggy dough forms.

Knead the Dough:

• Knead by hand or with a stand mixer for 6-7 minutes until smooth and elastic.
• If sticky, add up to 2 tbsp more flour (20g).

First Rise:

• Place dough in a greased bowl, cover, and let rise for 50 minutes or until doubled in size.

Incorporate Chocolate Chips:

• Gently punch down dough and knead in the chocolate chips.

Shape the Buns:

• Divide into 9 equal portions and roll into balls.
• Arrange in a greased 9×9-inch baking pan, leaving space between each.

Second Rise:

• Cover and let proof for another 25-30 minutes.

Bake:

• Preheat oven to 350°F (180°C).
• Brush buns with milk and bake for 19-23 minutes, until golden brown.

Finish:

• Brush with more milk while warm for a soft, glossy finish.
• Let cool slightly before serving.