In a large bowl, combine the flour, salt, sugar, and instant yeast. Mix well.

Add the cold, cubed butter to the flour mixture. Using a pastry cutter or your fingers, work the butter into the flour until the mixture resembles coarse crumbs.

Gradually add the cold water, mixing until a dough forms. Do not overmix.

Turn the dough out onto a lightly floured surface and shape it into a rectangle. Wrap in plastic wrap and refrigerate for at least 1 hour.

After chilling, roll the dough out into a larger rectangle, about 1/4 inch thick. Fold the dough into thirds like a letter, then wrap it again and refrigerate for another 30 minutes.

Roll the dough out again into a rectangle and fold it into thirds once more. Wrap and chill for another 30 minutes.

Preheat the oven to 400°F (200°C).

Roll the dough out to about 1/8 inch thick. Cut it into triangles (about 4 inches wide at the base).

Place a tablespoon of chocolate chips at the base of each triangle and roll the dough up towards the tip. Place the croissants on a baking sheet lined with parchment paper, seam side down.

Brush the tops with the beaten egg.

Bake for 15-20 minutes or until golden brown. Let cool slightly before serving.