In a large bowl, dissolve yeast in warm water. Add milk, eggs, butter, sugar, salt and 3 cups flour; beat on medium speed until smooth. Stir in enough remaining flour to form a soft dough.
Turn dough onto a floured surface; knead until smooth and elastic, 6-8 minutes. Place in a greased bowl, turning once to grease the top. Cover and let rise in a warm place until doubled, 1-1/2 to 2 hours.
Punch down dough. Turn onto a lightly floured surface; divide into 6 portions. Roll each portion into a 14-in. rope. For each loaf, braid 3 ropes together on a greased baking sheet; pinch ends to seal and tuck under. Cover with kitchen towels; let rise in a warm place until doubled, about 50 minutes. Preheat oven to 375°.
Beat together egg yolk and water; brush over loaves. Sprinkle with sesame seeds. Bake until golden brown, 30-35 minutes. Remove from pans to wire racks to cool.
Nutrition Facts
1 slice: 135 calories, 3g fat (1g saturated fat), 28mg