Proof yeast: In your stand mixer, or large bowl, stir together the warmed milk, yeast, and 1 teaspoon of the sugar. Let sit for 5-10 minutes until the yeast mixture becomes foamy and bubbly.

Make dough: In a bowl of your stand mixer with a paddle attachment, add in the eggs and melted butter and stir to combine. Then add in the rest of the sugar, flour, and salt, and stir to combine until a shaggy dough comes together.

Knead the dough: Fit the mixer with a dough hook attachment, and knead at medium speed for 6-8 minutes. If the dough is super sticky, add additional flour a little at a time if needed.

Let the dough rise: Lightly grease a large bowl, and place dough into the bowl, turning once to coat. Cover the bowl and allow it to rise until doubled in size, about 1 to 1 1/2 hours.

Prepare Pan: Grease or butter two 8×4′ loaf pans. Line the pans with parchment paper.

Make filling: Place butter, sugar, cocoa, and cinnamon in a mixing bowl and beat until combined. It should be a very soft paste that you will be able to spread easily.

Shape Babka: On a floured surface, roll dough into a rectangle about a 12×18 inch rectangle. Spread on the filling. Sprinkle with the chopped chocolate and press down lightly. Roll up the long side of the dough fairly tightly into a log, pinching the seam shut.

Proof: Cover the pans with greased plastic wrap and let rise at room temperature for 45 minutes to 1 hour. During the last 20 minutes of rising, preheat the oven to 350ºF.

Bake: Bake the bread in the oven for 40–50 minutes, or until 190ºF. Place on a wire rack and poke the bread several times with a long skewer.

Make the syrup: While the bread is baking, make the simple syrup. Combine 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.

Add syrup: Pour the cooled syrup over the babka a few tablespoons at a time. Let the babka cool in the pan for about 40 minutes, then use the parchment to lift out of the pans. Let cool completely on a wire rack.