Prepare the Dough:

• Activate Yeast: In a bowl, combine warm milk and yeast. Let sit for 5 minutes until foamy.​
• Mix Dough: In a large bowl, mix flour, sugar, and salt. Add yeast mixture and softened butter. Knead until smooth and elastic, about 5 minutes.​
• Chill Dough: Shape dough into a rectangle, wrap in plastic, and refrigerate for at least 6 hours or overnight.​

Prepare the Butter Block:

• Shape Butter: Place cold butter between parchment paper and pound into a 5×5-inch square. Chill until firm but pliable.​

Laminate the Dough:

• Encapsulate Butter: Roll dough into a 10×10-inch square. Place butter block diagonally in the center. Fold corners over butter, sealing edges.​
• First Fold: Roll dough into a 8×24-inch rectangle. Fold into thirds like a letter. Wrap and chill for 30 minutes.​
• Second and Third Folds: Repeat rolling and folding two more times, chilling 30 minutes between each fold.​

Shape the Croissants:

• Roll Dough: Roll laminated dough into a 8×32-inch rectangle.​
• Cut and Fill: Cut into 4×8-inch rectangles. Place a chocolate baton at one end and roll tightly, placing seam side down.​

Proof the Croissants:

• Let Rise: Place croissants on a baking sheet, cover, and let rise at room temperature until puffy, about 2 hours.​

Bake:

• Preheat Oven: Heat oven to 375°F (190°C).​
• Egg Wash: Whisk egg and milk; brush over croissants.​
• Bake: Bake for 18-20 minutes until golden brown.