Chocolate Babka

For the dough, stir flour, sugar, yeast, and salt together in the bowl of an electric mixer. Add eggs, yolk, milk, and vanilla using the dough hook. Mix on low speed until mixture comes together, scraping down the bowl and hook as needed. On low speed, add butter, 1 tablespoon at a time, until incorporated. Increase speed to medium and knead with the dough hook for about 10 minutes. The dough should have pulled away from the sides of the bowl.

Place the dough in an oiled bowl, turning the dough, so it is evenly coated. Cover with plastic wrap and refrigerate overnight.

The next day, remove dough from refrigerator while preparing for the filling and baking. Butter two 8 1/2 to 9-inch loaf pans. Line pans with parchment paper, cutting to fit with some overhang on both the long and short sides. Butter the bottom piece of parchment so that the top piece sticks. Line a cookie sheet with waxed paper.

Place butter, sugar, cocoa, and cinnamon in a mixing bowl and beat until combined.

Divide dough in half. On a floured surface, roll one dough half into a rectangle about 10 x 12-14 inches. The 10-inch side should be the closest to you. Spread half of the filling over the rolled dough. Sprinkle with half of the chopped chocolate. Starting with the end closest to you, roll the dough fairly tightly. Place seam side down on the cookie sheet. Repeat with reaming dough and filling.

Place the cookie sheet with the two rolls in the freezer for 15 minutes.

Remove the rolled dough from the freezer; trim the ends if they are uneven. Working one roll at a time, use kitchen shears to cut lengthwise down the center. Twist each roll, then braid the two pieces together, pinching the ends and place in one of the prepared pans. Repeat with the second roll. Don’t worry if the dough looks uneven in the pan.

Cover the pans with buttered plastic wrap and let rise at room temperature for 1 1/2 hours. During the last 20 minutes of rising, preheat the oven to 350ºF. Make the sugar syrup by combining the sugar and water in a pan. Bring to a boil over medium heat, stirring frequently. Let the mixture boil for a minute or two, then remove from heat to cool.

Once the rising time is finished, bake the breads in the oven for 40–50 minutes, or until 190ºF. Place on a wire rack and poke the breads several times with a long skewer. (Use the thermometer in a pinch.)

Pour the cooled syrup over the babkas 1/4 cup at a time, dividing the syrup evenly. Let the babkas cool in the pans for about 40 minutes, then using the parchment to lift out of the pans. Let cool completely on a wire rack.

Wrap cooled loaves in foil and store on the counter. Babkas may be wrapped well and frozen.