Step 1: Prepare the dough

• In a large mixing bowl, combine the flour, sugar, yeast, and salt.
• Add the warmed milk, softened butter, and eggs. Mix until a soft dough forms. Knead the dough on a floured surface for 8–10 minutes until smooth and elastic.
• Place the dough in a greased bowl, cover with a damp cloth, and let rise for 1–2 hours, or until doubled in size.

Step 2: Make the chocolate filling

• In a medium bowl, combine the chopped chocolate, melted butter, cocoa powder, and powdered sugar. Stir until smooth and spreadable.

Step 3: Prepare the streusel topping

• In a small bowl, mix the flour and brown sugar. Add the cold butter and use your fingers to form a crumbly mixture.

Step 4: Assemble the babka

• Punch down the dough and divide it in half. Roll one portion into a rectangle about 10×12 inches.
• Spread half of the chocolate filling evenly over the dough, leaving a 1-inch border. Roll the dough tightly into a log, then slice it lengthwise down the middle. Twist the two halves together and place in a greased loaf pan. Repeat with the second portion of dough.

Step 5: Let the babka rise

• Cover the loaf pans with a damp cloth and let rise for 1 hour, or until puffy.

Step 6: Bake the babka

• Preheat your oven to 350°F (175°C). Sprinkle the streusel topping evenly over the loaves. Bake for 35–40 minutes, or until golden brown and cooked through.

Step 7: Cool and serve

• Let the babka cool in the pans for 10 minutes, then transfer to a wire rack. Slice and serve warm or at room temperature.