Prepare the Pastry: First, gently unfold one sheet of the thawed puff pastry on a lightly floured surface.

Cinnamon Sugar Mixture: In a small bowl, combine the granulated sugar and ground cinnamon. Stir it well to make sure they're evenly mixed.

Butter and Sprinkle: Brush the melted butter evenly over the entire surface of the puff pastry. Then, sprinkle about half of the cinnamon-sugar mixture generously over the buttered pastry.

Cut into Triangles: Use a pizza cutter or a sharp knife to cut the pastry into triangles. I usually start by cutting the pastry in half lengthwise, and then cutting each half into 3 or 4 triangles. The size is up to you, smaller trianlges means smaller croissants.

Roll them Up: Starting at the wide end of each triangle, gently roll it up towards the point. Don't roll them too tightly, or they might not puff up properly.

Second Sheet: Repeat the steps 3-5 using the second puff pasty.

Arrange and Egg Wash: Place the rolled croissants on a baking sheet lined with parchment paper. Leave a little space between them, as they will expand while baking. Brush the tops of each croissant with the beaten egg.

Bake: Bake in a preheated oven at 375°F (190°C) for about 15-20 minutes, or until they are golden brown and puffed up. Keep an eye on them – oven temperatures can vary, so you might need to adjust the baking time slightly.

Cool and Enjoy: Once they're out of the oven, let them cool on the baking sheet for a few minutes before transferring them to a wire rack to cool completely. They're best enjoyed warm!