Mix flour, salt, sugar in large bowl.
Add yeast to one side of bowl.
Pour water gradually while mixing ingredients together.
Knead dough for 10 minutes until smooth.
Wrap dough tightly in plastic film completely.
Refrigerate dough for at least 1 hour.
Roll butter into rectangle between parchment paper.
Roll dough into rectangle twice butter size.
Place butter in center of dough rectangle.
Fold dough edges over butter completely encasing.
Roll out gently to original rectangle size.
Fold into thirds like folding a letter.
Wrap and chill for 30 minutes exactly.
Repeat rolling and folding process two times.
Roll final dough to 5mm thickness carefully.
Cut into triangles using sharp knife precisely.
Roll triangles from base to tip tightly.
Place on lined baking sheets with space.
Prove in warm place for 2 hours.
Brush with beaten egg before baking immediately.
Bake at 200°C for 20 minutes exactly.