In Leah Koenig's cookbook Modern Jewish Cooking: Recipes & Customs for Today's Kitchen

Ingreadients:

 

•  1 cup water, warmed to 115°
•  2 ¹⁄₄ tsp. active dry yeast
•  ¹⁄₂ cup sugar, plus 1 tsp.
•  4 ¹⁄₂ cups flour, plus more for dusting
•  1 tsp. kosher salt
•  3 eggs, lightly beaten
•  8 tbsp. unsalted butter, cubed and softened, plus more for greasing
•  ¹⁄₄ cup raspberry jam
•  2 tbsp. cocoa powder
•  2 tbsp. unsalted butter, at room temperature
•  8 oz. bittersweet chocolate, finely chopped
•  ¹⁄₂ cup sugar, divided
•  1 cup fresh raspberries, mashed

Direction

1. Make the dough: Combine water, yeast, and 1 tsp. sugar in a bowl until it begins to foam, about 10 minutes. Whisk flour and salt in a bowl; set aside. Add remaining sugar and eggs to yeast and whisk to combine; make a well in the center of the flour and add the yeast mixture. Mix to combine until a dough forms; turn dough out onto a lightly floured surface, and add butter, 2 pieces at a time, until a smooth dough forms. Place in a greased bowl and cover with plastic wrap; let rise in a warm place until doubled in size, about 1 hour.
2. Make the filling: Combine jam and cocoa powder in a small bowl; using your fingers, add butter until moist and crumbly and set jam mixture aside. Combine chocolate and 1⁄4 cup sugar in a bowl; set chocolate mixture aside.
3. Grease two 9" x 5" loaf pans; set aside. Divide dough into 2 balls; working with 1 ball of dough at a time and on a lightly floured surface, roll dough into a 12" x 10" rectangle, about 1⁄8" thick. Spread half of jam mixture over dough, leaving 1⁄4" border around the edge; sprinkle half of the chocolate mixture over the top. Starting at one of the short ends, roll dough up tightly; slice dough in half lengthwise, leaving 1⁄2" of dough connected at the top. Twist the strands together and pinch at the end to seal. (See gallery, below, for process shots.) Carefully place in prepared pan; repeat with remaining dough and filling. Cover loosely with plastic wrap and place in a warm area until doubled in size, 45 minutes more.
4. Make the syrup: Combine raspberries, remaining 1⁄4 cup sugar, and 2 tbsp. water in a 2-qt. saucepan over high; reduce heat and simmer until sugar has dissolved, 1–2 minutes. Remove from heat and let stand 10 minutes; strain through a fine mesh sieve, discarding solids.
5. Heat oven to 350°. Bake babkas, rotating halfway through, until golden and cooked through, 45-60 minutes. Remove from oven and immediately brush with syrup; allow babkas to cool in their pans for 20 minutes before transferring them to a wire rack to cool completely. Serve at room temperature.