In a large mixing bowl, combine all-purpose flour, granulated sugar, and salt. In a separate bowl, dissolve active dry yeast in warm milk, allowing it to bubble for about 5 minutes. Pour the yeast mixture and melted unsalted butter into the dry ingredients. Mix until a rough dough forms, then knead on a lightly floured surface for about 10 minutes until smooth. Wrap in plastic and refrigerate for 1 hour to firm up.

Place cold unsalted butter between two sheets of parchment paper. Use a rolling pin to pound it into a square about 6 inches by 6 inches, keeping it chilled.

Roll out the dough into a large rectangle, approximately 20 inches by 10 inches. Place the cold butter block in the center and fold the dough over to encase the butter completely. Roll this dough into a long rectangle, about 24 inches by 10 inches. Begin the first turn by folding the dough into thirds, like a letter. Wrap in plastic and refrigerate for 30 minutes.

Remove the dough from the fridge and roll it out again into a rectangle. Repeat the folding process for the second turn and chill for another 30 minutes. For the third and final turn, roll the dough out one last time and fold it again. Refrigerate for at least 1 hour.

Roll out the dough to about 1/4 inch thick and cut it into large triangles. Starting from the base, roll each triangle tightly towards the tip, tucking the tip underneath. Place each rolled croissant on a lined baking sheet with the point side down.

Cover the shaped croissants with a kitchen towel and let them rise at room temperature until noticeably puffy, about 1.5 to 2 hours.

Preheat your oven to 400°F (200°C). Prepare an egg wash by beating an egg and brushing it over the tops. Bake for 18–22 minutes until golden brown.

Remove the croissants from the oven and let them cool on a wire rack for a few minutes. Serve warm with butter, jam, or your favorite filling.