Prepare the Tangzhong by combining equal parts of water and bread flour in a saucepan and stir until a smooth paste forms, then cool.

Mix the dry ingredients: in a bowl, combine bread flour, sugar, salt, instant yeast, and milk powder.

Combine wet ingredients by adding the cooled Tangzhong, egg, and milk into the dry mixture.

Knead the dough on a floured surface for 12-14 minutes until smooth.

Proof the dough: shape into a ball, cover, and let rise until doubled.

Prepare the garlic butter spread by mixing softened butter, minced garlic, and salt.

Incorporate green onions by rolling out the dough, spreading the garlic butter, and sprinkling on chopped green onions.

Roll the dough tightly into a log and shape into a loaf, placing seam-side down in a greased pan.

Preheat the oven to 350°F and brush the loaf with the egg wash.

Bake the bread for 25-30 minutes until golden brown.

Cool the bread: allow it to cool in the pan for 5 minutes, then transfer to a rack.