We pour in the mixer lukewarm milk and we put inside the sugar and the yeast and we mix well. We wait until it rises and then we add the flour, the salt, and the egg and we start kneading with the hook on a medium speed and after two minutes we turn the mixer on a high speed until we have a dough that easily pulls back from the sides of the bowl. Then, we add the cooled butter and we knead at a high speed for 10 minutes until the butter homogenizes with the dough. We wrap the dough with a warm towel and we leave it to rest until it becomes twice the size. We separate it into 6 pieces and we place them in a buttered baking pan (30x6cm). We leave it again to rest until it becomes twice the size, we spread with the egg and we bake for 13-15 minutes at 170 degrees.