Make the Dough: In a large mixing bowl, whisk together the flour, yeast, sugar, and salt.

Add the lukewarm milk and water. Mix until a shaggy dough forms.

Turn the dough out onto a lightly floured surface and knead for about 5-7 minutes, until it becomes smooth and elastic.

First Rise: Shape the dough into a ball, place it back in the bowl, and cover it with plastic wrap or a damp kitchen towel. Let it rise in a warm place for about 1-1.5 hours, or until doubled in size.

Prepare the Butter Block: While the dough is rising, place the cold butter between two sheets of parchment paper. Using a rolling pin, pound and roll the butter into a 6x8 inch rectangle. Keep it chilled.

Laminate the Dough (First Turn): Once the dough has doubled, punch it down to release the air. Roll it out into a 12x16 inch rectangle.

Place the cold butter block in the center of the dough, leaving a border around the edges.

Fold the dough over the butter like a letter, enclosing the butter completely. Pinch the seams to seal.

Roll and Fold (First Turn): Gently roll the dough out into a 24-inch-long rectangle. Be careful not to press too hard, or the butter might break through.

Fold the dough in thirds, like a letter again. This is your first "turn." Wrap the dough in plastic wrap and chill in the refrigerator for 30 minutes.

Second and Third Turns: Repeat the rolling, folding, and chilling process two more times. Each time, rotate the dough 90 degrees before rolling. This ensures even layers. So, roll, fold, chill for 30 minutes, then repeat one last time.

Final Chill: After the third turn, wrap the dough tightly and chill for at least 2 hours, or preferably overnight. This allows the gluten to relax and the butter to firm up, making it easier to shape.

Shape the Croissants: On a lightly floured surface, roll the chilled dough out into a large rectangle, about 1/8 inch thick.

Using a sharp knife or pizza cutter, trim the edges to make a clean rectangle.

Cut the dough into triangles. Each triangle should be about 4-5 inches wide at the base.

Roll the Croissants: Starting at the base of each triangle, gently stretch the dough, then roll it up towards the tip.

Place the rolled croissants on a baking sheet lined with parchment paper, leaving some space between them. Curve the ends slightly to create a crescent shape.

Final Proof: Cover the croissants loosely with plastic wrap and let them proof in a warm place for 1-2 hours, or until they are puffy and almost doubled in size.

Egg Wash: Preheat your oven to 375°F (190°C). Gently brush the proofed croissants with the beaten egg.

Bake: Bake for 18-22 minutes, or until the croissants are golden brown and cooked through. Rotate the baking sheet halfway through to ensure even browning.

Cool: Let the croissants cool on a wire rack for a few minutes before serving. They are best enjoyed warm!