1/2 cup milk (lukewarm, about 115°F)
granulated sugar (2 tablespoons for bread, 3 tablespoons for syrup)
1 tablespoon active dry yeast
bread flour (3 cups, divided, plus more for dusting, for bread; 1 tablespoon for filling)
1 teaspoon salt
1 egg yolk
1/2 cup butter, softened (1 stick, cut into 1 in. pieces for bread)
3 oz. semisweet chocolate (chopped)
6 tablespoons butter
2 tablespoons confectioners’ sugar
2 tablespoons cocoa powder
2 tablespoons water
In large bowl, stir together milk, 2 Tbsp sugar and yeast until dissolved. Let stand 10 minutes or until foamy. Stir in 1/2 cup flour.
In large bowl, stir together remaining 2 1/2 cups flour and salt.
Beat yeast mixture with paddle attachment of electric mixer on low speed, adding eggs and yolk one at a time, beating well after each addition. Switch to dough hook. Add flour mixture and mix on low speed until well combined. Gradually mix in 1/2 cup butter, beating well after each addition on medium speed until fully incorporated, about 10 minutes. Dough will be very sticky. Cover and let rise at room temperature until doubled in size, about 1 hour.
To prepare filling, in medium microwave-safe bowl, combine chopped chocolate and 6 Tbsp butter. Melt on half (50%) power 60 seconds; stir. Continue melting in 30 second intervals, stirring between each, until fully melted and smooth. Whisk in confectioners’ sugar, cocoa powder and 1 Tbsp flour until smooth.
Prepare 9 in. x 5 in. loaf pan with vegetable pan spray. Preheat oven to 350°F.
Transfer dough to heavily floured surface. Knead dough until smooth; cover and let rest 10 minutes. On lightly floured surface, roll dough out to a 20 in. x 12 in. rectangle. Spread filling evenly over dough surface. Roll up from long end as for cinnamon rolls, pinching seam to seal. Carefully cut log in half lengthwise. Twist pieces together and place in prepared pan in an “S” shape, tucking ends under. Cover pan and let rise in a warm area 30 minutes.
To prepare sugar syrup, combine 3 Tbsp sugar and water in a small microwave-safe bowl. Microwave on high in 15 second intervals, stirring between each, until sugar has dissolved.
Uncover loaf and bake 32 to 37 minutes or until loaf is golden brown and sounds hollow when tapped. Let cool in pan on cooling grid 5 minutes, then turn out onto grid. Brush loaf with sugar syrup while it is still hot, then let loaf cool completely before cutting and serving.