Chocolate Babka

In a large bowl, mix 2 cups flour, sugar, yeast and salt. Cut in butter until crumbly. In a small saucepan, heat water to 120u0b0-130u0b0; stir into dry ingredients. Stir in eggs and yolk, orange zest and enough remaining flour to form a soft dough (dough will be sticky).
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 refrigerate 8 hours or overnight.
Turn out dough onto a lightly floured surface; divide in half. Roll each half into a 12x10-in. rectangle. For filling, in a microwave, melt butter and chocolate chips; stir until smooth. Stir in confectioners' sugar, cocoa and salt. Spread filling to within 1/2 in. of edges. Roll up jelly-roll style, starting with a long side; pinch seam and ends to seal.
Using a sharp knife, cut each roll lengthwise in half; carefully turn each half cut side up. Loosely twist strips around each other, keeping cut surfaces facing up; pinch ends together to seal. Place in 2 greased 9x5-in. loaf pans, cut side up. Cover with kitchen towels; let rise in a warm place until almost doubled, about 1 hour.
Preheat oven to 375u0b0. Bake until golden brown, 35-45 minutes, tenting with foil halfway through. Meanwhile, in a saucepan, combine sugar and water; bring to a boil. Reduce heat; simmer, uncovered, 10 minutes. Brush over warm babka. Cool 10 minutes before removing from pans to wire racks.