Prep your filling. In a small saucepan add the chocolate, the hazelnut nougat (cut into small pieces) and the whipping cream and place on medium-low heat. Stir with a silicone spatula until everything is melted and combined, then set aside.
Meanwhile add the hazelnuts to a food processor and whizz until creamy. Transfer to the nougat-chocolate mixture and mix until combined.
Take some candied orange peel from your jar and cut into small pieces. Check notes for recipe link.
Take the dough out of the fridge and transfer to your oiled working surface. With a lightly oiled rolling pin roll the dough into a rectangle (about 0.5-1cm. thick).
Spread the filling onto 3/4 of the surface of your dough sheet, so it can stick together and close at the end. Sprinkle the orange peel and then start rolling it, like you’d do with a cinnamon roll. Place on a cutting board lined with lightly oiled baking paper and set into the freezer for 30-40min.
Line the loaf pan with baking paper and set aside. Take the roll out of the freezer and cut it lengthwise, to expose the layers. Place the two parts in a cross, then start braiding towards the edges, forming a spiral, with the layers exposed. Come the edges together and turn under the formed loaf. Transfer the babka into the lined pan. Cover with a tea towel and let proof in a warm place for 1h 1/2 to 2h, or until it rises above the edge of the pan. Then turn on the oven and heat at 200C.
Lightly beat the egg/ egg wash with milk, then brush the babka before baking. Bake for around 40 minutes in the preheated oven (fan off), or until the top becomes dark brown and a skewer comes out clean of raw dough.
If you're not using/ adding homemade candied orange, you'll need to make some syrup while the babka is baking. In a small saucepan add 20g sugar and 20g water and place on medium heat until the sugar dissolves. Then slowly boil for a few minutes until syrupy, add a couple peels from a lemon or orange and set aside.
Take the loaf out of the oven and brush hot with the orange or and let cool in the tin for an hour. Then remove from tin and cool completely on a cooling rack. Do not cut until it has cooled down. Enjoy next to a glass of warm milk or tea!