Dissolve the yeast in 1/2 the warm milk with the sugar. Pour in a little flour and leave for 10 min. In the meantime, sift the rest of the flour with the salt in a bowl and make a well.
Beat 2 eggs and 1 egg white. Pour the eggs, yeast and remaining milk into the well. Knead a soft dough. While kneading, pour in the olive oil a spoon at a time until fully absorbed.
Form the dough into a ball. Put it in an oiled bowl, cover and leave for about 1 hour to rise, or until doubled in volume.
Once ready, roll the dough out on a floured surface into a rectangle. Smear it with olive oil. Wrap it into a roll. Cut it down the middle but not all the way through (leave it connected).
Weave the 2 parts together like a braid, pinching the cut off ends together. Wrap into a spiral and place in an oiled form with removable sides (10 1/4″ (26 cm) diameter). Leave it for about 15 min. to rise.
Smear with the yolk beaten with the milk. Bake in a preheated 356°F (180 °C) oven about 40 min. After you take it out, smear with the lump of butter and cover with a tower to smother.
Adapted from evatoneva.com.