Remove the milk and butter from the refrigerator. Cut the butter into tablespoon cubes and set aside.

Spray a large mixing bowl with cooking spray and set aside.

In the work bowl of the stand mixer, add 3 ½ cups of flour. Add the sugar and salt on one side of the bowl. Stir to combine.

If using instant yeast, add the yeast on the other side of the bowl. If using active dry yeast, sprinkle it over the room temperature water in a liquid measuring cup and allow it to proof for 3 to 5 minutes.

Pour the water and milk over the flour. Mix the dough on medium-high speed until smooth, about 8 to 10 minutes.

Remove the dough from the mixer, form into a smooth ball, and place in the prepared mixing bowl. Cover with plastic wrap and rest in a warm place for at least 30 minutes.

Wipe out the work bowl and attach the paddle attachment. Add the cubed butter and 2 tablespoons of flour and beat until smooth and creamy.

Shape the butter into a flat square, wrap it in plastic wrap, and chill in the refrigerator while the dough is proofing.

Once the dough has proofed, pour it onto a floured work surface and roll into a square, approximately 10-inch x 10-inch.

Place the chilled butter square diagonally in the center of the dough and fold the corners of the dough over the butter, pinching the seams closed.

Refrigerate the dough for 60 minutes.

Roll the dough into a 16-inch x 8-inch rectangle. Fold into thirds like a letter. Place back on the baking sheet and refrigerate for 60 minutes.

Repeat the rolling, folding, and refrigerating process two more times, for a total of 3 turns. After all turns, wrap the dough in plastic wrap and refrigerate overnight.

Remove the chilled dough and place it on a lightly floured surface. Cut the rectangle in half and place one half back in the fridge.

Roll the dough into a 13-inch wide x 10-inch tall rectangle, about 1/4 inch thick. Trim the edges.

Cut notches in the dough and then cut the dough into triangles. Start with the wide end and roll up to the point.

Repeat the steps for the other half of the dough in the fridge.

Final proof the shaped croissants on prepared baking sheets for 60 to 90 minutes until doubled in size.

Preheat the oven to 375°F.

Brush the beaten egg on each croissant and bake for 20 minutes, rotating pans halfway through.