01 -
Stir warm milk, yeast, and 1 tablespoon of the sugar in a small bowl. Let stand for 10-15 minutes until foamy.
02 -
In a stand mixer bowl, combine flour, remaining sugar, and salt. Add the egg, egg yolk, vanilla, and yeast mixture. Knead with the dough hook on low for 2 minutes, then on medium for 8-10 minutes.
03 -
Add softened butter one tablespoon at a time, kneading until each piece disappears before adding the next. Continue kneading for 4-5 minutes until the dough is smooth and elastic.
04 -
Transfer the dough to a lightly greased bowl, cover, and let rise until puffy, about 60-75 minutes. Press into a rectangle, wrap, and refrigerate for at least 1 hour or overnight.
05 -
Roll chilled dough on a lightly floured surface into a 14x12 inch rectangle. Spread Nutella over the surface, leaving a 1/2 inch border. Sprinkle with chopped hazelnuts and cocoa powder if using.
06 -
Roll tightly from the long side into a log. Chill for 20-30 minutes, then cut lengthwise. Slice into 10 pieces and twist each piece into a loose knot or coil with the cut layers facing up. Place on a parchment-lined baking sheet or in a greased muffin pan.
07 -
Cover and let rise until puffy, 35-50 minutes. Brush lightly with egg wash. Bake at 350°F (175°C) for 20-24 minutes until deeply golden and cooked through.
08 -
While the buns bake, simmer sugar and water until dissolved. Brush the hot buns with the syrup, then cool for at least 15 minutes before serving.