In a mixing bowl, combine the flour, sugar, and salt. Mix the dry ingredients thoroughly.

Add the cold butter to the flour mixture. Use a pastry cutter or your fingers to blend until the mixture resembles coarse crumbs.

Gradually pour in the cold water while mixing with a fork to form a dough.

Wrap the dough in plastic wrap and refrigerate for about 15 minutes.

On a lightly floured surface, roll the dough out into a rectangle about 1/4 inch thick.

Fold the dough into thirds, like a letter. Roll it out again into a rectangle and repeat this folding process two more times.

After the final fold, roll out the dough into a larger rectangle. Cut it into triangles and roll each triangle from the base to the tip.

Place the shaped croissants on a baking sheet lined with parchment paper. Brush with beaten egg and bake at 400°F (200°C) for about 15 minutes, or until golden brown.