Step 1: Prepare the Dough

In a bowl, dissolve the yeast and sugar in warm milk. Let it sit for 5-10 minutes until foamy.

In a large mixing bowl, combine the flour and salt.

Add the softened butter, egg, and yeast mixture to the flour. Knead for about 8-10 minutes until a smooth, elastic dough forms.

Cover the dough and let it rise in a warm place for about 1-1.5 hours or until doubled in size.

Step 2: Prepare the Butter Layer

Place the cold butter between two sheets of parchment paper and roll it into a thin rectangle, approximately 20×25 cm (8×10 inches).

Chill the butter while rolling out the dough.

Step 3: Incorporate the Butter

Roll out the risen dough on a lightly floured surface into a rectangle twice the size of the butter sheet.

Place the butter in the center and fold the dough over it like an envelope. Seal the edges.

Roll out the dough carefully into a long rectangle and fold it into thirds (like a letter).

Wrap in plastic wrap and chill for 30 minutes. Repeat this process two more times, chilling in between.

Step 4: Shape the Gipfeli

Roll out the dough to about 5mm (¼ inch) thick.

Cut into triangles (about 8×20 cm or 3×8 inches).

Roll each triangle from the base to the tip to form a crescent shape.

Place them on a baking sheet lined with parchment paper, cover, and let rise for 30-45 minutes.

Step 5: Bake the Gipfeli

Preheat the oven to 200°C (390°F).

Mix the egg yolk with milk and brush it over the Gipfeli for a golden crust.

Bake for 15-18 minutes until golden brown and flaky.

Let cool slightly before serving.