The authentic Sicilian brioche recipe.
Add the butter and start kneading. Add 1 egg and knead until totally absorbed.
Cover it with a kitchen cloth and let rise 2 hours. If it's Winter, place the bowl inside the oven with the light on and a kettle with boiling water next to it, this will help it leaven.
Divide the dough into 6 pieces. Tear off a small piece from each and form two balls, by working the dough with your hands: a big one and a tiny one, called “tuppo”. It will be a sticky dough so work it on a floured surface and add some flour to the dough if needed, but as little as you can.
Put the big balls on an oven sheet, lined with parchment paper. Place the small balls on top of the big ones and press a little to fix them.
Let the brioches rise two hours, covered with a cloth (inside the oven if it's Winter).
Mix the remaining egg with two tablespoons of milk. Brush the brioches's surface with the egg mixture.
Bake 15-17 minutes, until golden brown.