In a bowl, combine the warm milk and granulated sugar, then sprinkle the yeast over the top. Let it sit for about 5-10 minutes until foamy.
In a large mixing bowl, whisk together the flour and salt. Make a well in the center and add the yeast mixture, softened butter, and eggs. Mix until a soft dough forms.
Knead the dough for about 10 minutes on a lightly floured surface, until smooth and elastic. Place the dough in a greased bowl, cover it with a damp dish towel, and let it rise in a warm place for 1-2 hours or until doubled in size.
Once the dough has risen, punch it down and roll it into a rectangle about 1/4 inch thick. Spread the chocolate hazelnut spread evenly over the surface, then sprinkle with cocoa powder and chopped hazelnuts.
Starting from one edge, roll the dough tightly into a log. Cut the log in half lengthwise, exposing the layers. Twist the two halves together and form a braid, tucking the ends under.
Place the twisted dough into a greased loaf pan. Cover again and let it rise for another 30-40 minutes.
Preheat your oven to 350°F (175°C). Once the dough has risen, bake for 25-30 minutes, until golden brown and cooked through.
Let the babka cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. Dust with powdered sugar before serving.
Notes
Slice the babka and arrange it on a beautiful serving platter. Garnish with a few whole hazelnuts for an elegant touch and serve with an extra dollop of chocolate hazelnut spread on the side.