Mix the dry ingredients (bread flour, sugar, yeast, salt) together.
Add the melted butter, warmed milk, and egg yolks, and mix to form a dough.
Knead the dough for 10 minutes until smooth and elastic.
Place the dough in an oiled bowl, cover, and let rise for 1-2 hours.
Divide the dough into 4 quarters, roll each into a circle, and layer them with Nutella in between.
Cut the layered dough into segments, twist them, and pinch the edges together to form a flower shape.
Brush the top with the reserved egg whites.
Bake at 180°C / 350°F for 15-20 minutes until golden brown.
