Cut the butter into small pieces and let it come to room temperature; sift the flour and set aside. Pour the regular dry yeast into about 1/3 cup (80ml) of warm water at 80°F (26°C) and let it sit for 5 minutes to activate.

Mix the all-purpose flour, granulated sugar, salt, egg, and activated yeast mixture in a bowl. Gradually add the remaining 1/3 cup (80ml) of water, depending on the flour's absorption, and knead into a non-sticky dough.

Use a hand mixer on medium speed to knead the dough for 3 minutes until smooth. Add the cut butter and continue kneading on medium speed for another 3-4 minutes until the dough can be stretched into a thin film.

Shape the dough into a ball and place it in a greased bowl. Cover with plastic wrap and let it rise in a warm place for 1-1.5 hours. Once risen, punch down the dough to release air, divide it into two equal parts, shape into balls, cover with plastic wrap, and let rest for 15 minutes.

Roll the rested dough into a rectangle, spread a layer of hazelnut chocolate spread, and roll it up from the shorter side, pinching the seam tightly and placing it seam-side down. Let it rise in a warm place for a second fermentation for 50 minutes.

Once doubled in size, brush with a layer of milk and bake in a preheated 350°F (170°C) oven for about 30 minutes.