Bring milk to lukewarm temperature. To half of the milk add the yeast, 2tablespoons flour and 1tablespoon sugar. Mix together well. Let this starter rest for 10 minutes.
Mix the rest of the flour and the butter till the mixture forms crumbs. Then add the rest of the milk and the yeast mixture with egg yolks, remaining sugar and the salt. Mix well in a bowl. Knead and mix for 10 to 12 minutes.
Let the dough rest till it doubles in bulk, 45 minutes to 1 hour.
Put the dough on a floured board and cut into 3parts. Roll each part to a narrow strip about 15inches long.
Braid the strips to form a long loaf. Put it on a buttered baking sheet 17 by 12inches. Preheat oven to 375°F.
Beat the extra egg yolk with 1teaspoon water. Brush the loaf with egg-yolk glaze, and put it aside until the glaze becomes dry, 10 to 15 minutes in a 72°F. room. Or you can put your hand on it and feel when the glaze is dry.
Now brush the loaf with egg white. Bake in the preheated oven for 40 minutes.