Put lukewarm milk, yeast, and sugar in a stand mixer bowl, then whisk well. Let it sit for 5 minutes.

Combine bread flour and cake flour, and add to the milk mixture. Add salt and milk powder, and start the mixer kneading with a dough hook at medium speed.

When the dough is becoming a ball (after about 8 minutes), add soft butter and knead for another 4-5 minutes until the butter is completely incorporated. Cover with plastic, and leave in a warm place about 1 hour until the dough has doubled in size.

Take the dough and push gently to deflate the gas from the dough. Put on to a cutting board, and cut into 8 equal pieces about 2.5oz (or 70g) each. Form into small balls. Let them rest for 15 minutes covered.

Place shaped dough balls on a baking sheet lined with parchment paper, leaving 2" (or 5cm) space between the balls. Brush egg wash (the mixture of egg with a pinch of salt) on the surface of the dough, and sprinkle some sugar on top. Leave them to double in size, about 1 hour.

Bake in a preheated oven at 400F(205C) for about 9 minutes until they brown.