Mix flour, yeast, salt, water, and melted butter in a mixer for eight minutes.
Shape the dough into a ball and let it rise in an oiled bowl for one hour.
Roll the cold butter block into a 14cm square between greaseproof paper and chill.
Roll dough to a 20cm square and wrap the butter inside like an envelope.
Roll into a 45x15cm rectangle, fold into thirds, and chill for 30 minutes.
Repeat the rolling, folding, and 30-minute chilling process two more times.
Roll out again, sprinkle with sugar, fold, then roll to a 40x30cm rectangle and cut into 12 squares.
Place squares in a greased muffin tin, sprinkle with sugar, and rise for 30 minutes.
Bake at 220°C for 30 to 40 minutes until golden brown.
Cool briefly on a wire rack before serving warm or cold.