Sift the flour into a bowl and form a well. Add yeast, sugar, and lukewarm milk to the well, mix lightly, and let activate for 10–15 minutes. Add the egg, butter, and salt, then knead everything into a smooth, elastic dough. Cover and let rise in a warm place for 60 minutes until doubled in size.
Mix the hazelnuts, sugar, cinnamon, cream, and honey into a spreadable filling.
Roll the dough into a 30 x 40 cm rectangle. Spread the filling evenly, fold the top half towards the center, and then fold the bottom half over it to create a long rectangle. Lightly roll it to flatten and create space for braiding.
Cut the rectangle into 6 strips. For each strip, make two cuts to divide it into three strands connected at the top. Braid the strands and roll into coils.
Place the braids in a loaf pan lined with parchment paper, arranging them slightly offset. Let rise again for 30–40 minutes.
Brush with egg yolk and, if desired, sprinkle with chopped hazelnuts. Bake in a preheated oven at 180°C (160°C fan) for 30–35 minutes until golden brown. Cool and dust with powdered sugar before serving.
