Activate the Yeast: In a large bowl, combine the warm milk, yeast, and 1 teaspoon of sugar. Let sit for 5-10 minutes, until foamy.

Make the Dough: Add the remaining sugar, salt, and softened butter to the yeast mixture. Stir until combined. Gradually add the flour, mixing until a shaggy dough forms. Turn the dough out onto a lightly floured surface and knead for about 8-10 minutes, until smooth and elastic.

First Rise: Place the dough in a lightly greased bowl, turning to coat. Cover with plastic wrap and let rise in a warm place for about 1 hour, or until doubled in size.

Prepare the Butter Block: While the dough is rising, arrange the cold butter slices between two sheets of parchment paper. Using a rolling pin, pound the butter into a rectangle that is about 1/4 inch thick. Set aside in the refrigerator to keep cold.

Laminate the Dough: Punch down the risen dough and roll it out on a lightly floured surface into a rectangle about 12×18 inches. Place the butter rectangle in the center of the dough. Fold one side of the dough over the butter, then fold the other side over the first fold, enclosing the butter.

First Turn: Gently roll the dough into a rectangle again. Fold into thirds (like a letter), and rotate the dough 90 degrees. Wrap in plastic wrap and refrigerate for 30 minutes.

Second Turn: Repeat the rolling and folding process (rolling, folding into thirds, rotating) and refrigerate for another 30 minutes.

Third Turn: Repeat the rolling and folding process (rolling, folding into thirds, rotating) and refrigerate for another 30 minutes.

Shape the Gipfeli: Roll the dough out into a large rectangle, about 1/8 inch thick. Using a sharp knife or pizza cutter, cut the rectangle into long triangles. Roll each triangle from the wide end towards the point, then slightly curve to form a crescent shape.

Second Rise: Place the shaped Gipfeli on baking sheets lined with parchment paper. Cover loosely and let rise in a warm place for another 30-45 minutes, until slightly puffy.

Preheat and Egg Wash: Preheat your oven to 400°F (200°C). In a small bowl, whisk together the egg and milk for the egg wash. Lightly brush the top of each Gipfeli with the egg wash.

Bake: Bake in the preheated oven for 15-20 minutes, or until golden brown and flaky. Let cool on a wire rack before serving.