Step 1: Prepare the Dough

1. In a small bowl, combine warm milk, sugar, and yeast. Stir gently and let it sit for 5-10 minutes until foamy.
2. In a large mixing bowl, combine flour and salt.
3. Add the yeast mixture, melted butter, and egg to the flour mixture. Mix until the dough starts forming.
4. Transfer to a lightly floured surface and knead for 8-10 minutes until smooth and elastic.
5. Place the dough in a greased bowl, cover with a cloth, and let it rise in a warm place for 1-1.5 hours until doubled in size.

Step 2: Roll and Shape the Gipfeli

1. Once risen, punch down the dough to remove air bubbles.
2. Roll out the dough into a large rectangle (about 1/4 inch thick).
3. Cut the dough into long triangular pieces (about 3 inches wide at the base and 6 inches tall).
4. If adding filling, place a small amount of chocolate, almond paste, or cheese at the base of each triangle.
5. Roll each triangle from the wide base to the tip to form a crescent shape.

Step 3: Let the Gipfeli Rise Again

1. Place the shaped Gipfeli on a parchment-lined baking sheet, ensuring the tip is tucked under to prevent unrolling.
2. Cover loosely with a towel and let them rise for 30-40 minutes.

Step 4: Apply Egg Wash and Bake

1. Preheat the oven to 375°F (190°C).
2. In a small bowl, whisk together 1 egg yolk and 1 tbsp milk to make an egg wash.
3. Brush each Gipfeli with the egg wash for a golden finish.
4. Bake for 15-18 minutes, or until golden brown and crisp.

Step 5: Serve and Enjoy

1. Allow Gipfeli to cool slightly before serving.
2. Enjoy with coffee, tea, or hot chocolate for a classic Swiss breakfast!