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1
Grind the poppy seeds in a spice or coffee grinder, working in batches if necessary, until powdery, 10 to 20 seconds per batch. In a small saucepan set over medium heat, add the ground poppy seeds, cocoa powder, sugar, milk, coffee, and a pinch of salt. Bring to a low boil, then lower heat to medium-low and cook, stirring frequently, until the mixture thickens, 7 to 10 minutes. Stir in the vanilla and continue cooking, stirring constantly, until mixture is very thick (it will still look a little liquidy and will continue to thicken as it cools), 2 to 3 minutes.
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2
Remove from heat and immediately stir in the orange juice. Transfer filling to a bowl, cover, and chill in the fridge until it thickens into a spreadable paste, at least 1 hour. (The filling can be made up to 3 days in advance. Store, covered, in the fridge until needed.)
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3
Preheat oven to 350u00b0 F and line a large, rimmed baking sheet with parchment paper. Stir together the yeast, 1 teaspoon sugar, and warm water in a small bowl and let sit until bubbling and frothy, 5 to 10 minutes.
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4
Meanwhile, add the flour, remaining 1/4 cup sugar, salt, orange juice, 2 eggs and 1 egg yolk (reserve the white), and butter to the bowl of a standing mixer fit with the paddle attachment. When the yeast mixture is bubbling, pour it into the bowl and mix on low speed until the dough just comes together. Turn the dough out onto a lightly floured surface and knead briefly until the butter is fully dispersed, 2 to 3 minutes.
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5
Cut the dough into 2 equal pieces, and keep 1 piece in the bowl, covered, while working with remaining piece. Roll out the dough into a large, 1/8-inch thick rectangle. Spread half of the chocolate-poppy seed mixture evenly over the rectangle, leaving a 1/2-inch border. Brush the border with a little of the reserved egg white to help seal the dough. Starting at one of the short sides, roll up the dough like a jelly roll (not too tight), pinch the ends to seal, and place it, seam side down, on the prepared baking sheet. Repeat the filling and rolling process with the remaining dough and filling and place the roll on the baking sheet, leaving 2 inches of space between the two rolls. Brush the tops of each roll with egg wash and prick in a few places with a fork to keep it from splitting while it bakes.
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6
Bake, rotating the pan once halfway through, until golden brown and cooked through, 30 to 35 minutes. (Some of the filling might leak out during baking, that's okay.) Remove from oven and transfer kokosh to wire racks to cool slightly. Serve warm. Store leftovers, tightly wrapped in plastic, for up to 1 week. Reheat leftover kokosh briefly in a toaster oven or oven before serving.
