Dissolve the yeast in the lukewarm water, mix the flour with the salt, pour in the water and knead for 8-10 minutes into a smooth dough. Chill for 30 minutes.
Flatten the butter between two sheets of baking paper into a 15×15 cm slab and chill.
Roll the dough into a square, wrap the butter in it like an envelope, roll into a long rectangle and fold in three. After chilling for 20-30 minutes, repeat.
Before the third fold, sprinkle most of the sugar over the dough and worktop, and roll and fold it in three like that.
Butter an 8-hole muffin tin and sprinkle it with sugar. Roll the dough into a rectangle about 5 mm thick and cut it into 8 squares of 10×10 cm.
Fold the four corners of each square into the middle, press down and settle them in the tin. Sprinkle with the rest of the sugar and leave to rise covered for 45 minutes.
Bake at 180 °C for 25-30 minutes until deep caramel brown. Lift them out of the tin after 5 minutes (later they'll stick) and cool on a rack.
A Receptnaptár original recipe. Calories and protein are estimated.