To prepare the brioche dough, combine the yeast, confectioner’s sugar, salt, milk powder and flour in the bowl of a stand mixer. Combine the frozen cranberries with the sugar and mix well. Reserve.
On medium speed, add the eggs and the yolk. Knead for 3-5 minutes, or until the dough is smooth and elastic. Begin adding the butter, a little at a time, until it has been completely absorbed by the dough. Increase the mixer to high speed and knead for approximately 1 minute. Finally, reduce the speed to low and add the cranberries.
Scrape the dough away from the sides of the mixing bowl, and turn out onto a lightly floured surface. Shape into a ball, and place in an oiled mixing bowl. Be sure that the bowl is at least twice the size of the fresh dough, as it will rise over time. Cover and refrigerate overnight.
Shape the loaves and allow to proof, covered at room temperature, until tripled in size. Set the oven at 350°F/176°C.
Brush the loaves with beaten egg. Bake on the middle rack of the oven for 35-45 minutes, or until richly browned. Cool thoroughly before slicing.