Cover bowl with cling wrap and chill for 12 hours.
Prepare the dough
In a mixer fitted with a bread hook, add flour, yeast, sugar, egg and water. Start mixing at slow speed for 2 minutes. Add salt and continue to knead until dough lifts from the wall of the mixing bowl.
Add the water roux mixture and continue kneading for 3 minutes.
Add butter and increase the kneading speed to medium.
Knead for 25 minutes or until dough is no longer sticky and does not break when pulled to perform windowpane test.
Proof the dough
Place dough in a slightly oiled bowl. Cover with cling wrap and leave it to proof in a warm area for 45 minutes.
With lightly floured hands and tabletop, knead proofed dough into a smooth round ball. Divide dough into 10 balls of about 40g each.
Roll each small ball into a round shape and leave to proof for 70 minutes.
Bake and decorate the buns
Brush with egg white, then bake at 185°C for 6-8 minutes until it turns brown.
Leave it to cool for 15 minutes.
Smear some mayonnaise on the edges of each bun, then sprinkle the chicken floss onto the mayonnaise.
Draw on the features using the melted chocolate in a piping bag.
Use a small amount of the melted chocolate to stick the edible hearts on as bow.