Dissolve yeast in warm water in a small bowl. Let stand for about 5 minutes or until foamy.
In a large mixing bowl, combine warm milk, softened butter, egg, sugar, and salt. Stir well.
Stir in the yeast mixture. Add 3 cups of flour and mix until incorporated. Gradually add little by little of the remaining flour just until the dough gathers into a ball.
Turn the dough onto a floured surface and knead for about 6-10 minutes, or until smooth and elastic.
Place the dough in a bowl, cover with plastic wrap, and let rise in a warm place for 1 to 1 and 1/2 hours until doubled in size.
After rising, deflate the dough gently and divide into 50-55 portions. Form each portion into a ball and arrange in a greased 9×13 inch baking pan.
Cover the pan loosely with plastic wrap and let the buns rise for another hour.
Preheat oven to 350°F (175°C). Combine milk powder and sugar in a bowl and mix well.
Beat an egg and brush it over the buns. Sprinkle half of the milk-sugar mixture over the buns.
Bake for 17-20 minutes or until golden. Cool slightly and sprinkle the remaining milk-sugar mixture.