Follow these detailed steps to create your very own Charcoal-Dough Croissants with Salted Egg Yolk Lava:

1. Prepare the Dough: In a large mixing bowl, combine the all-purpose flour, activated charcoal powder, salt, sugar, and instant yeast. Mix well.
2. Incorporate Wet Ingredients: Add the warmed milk and egg to the dry mixture. Stir until a rough dough forms.
3. Knead the Dough: Transfer the dough to a floured surface and knead for about 5 minutes until smooth.
4. Chill the Dough: Wrap the dough in plastic wrap and refrigerate for at least 30 minutes.
5. Prepare Butter Block: While the dough chills, prepare the butter by placing the cold, cubed butter between two sheets of parchment paper. Use a rolling pin to flatten it into a rectangle about ½ inch thick. Refrigerate again until firm.
6. Roll Out the Dough: After chilling, roll out the dough into a rectangle about twice the size of the butter block.
7. Encase the Butter: Place the butter block in the center of the rolled dough and fold the dough over to enclose the butter completely.
8. Laminate the Dough: Roll out the dough into a long rectangle, then fold it into thirds like a letter. Repeat this process two more times, chilling the dough for 15 minutes between each fold.
9. Prepare the Filling: In a small bowl, mix the salted egg yolks with the heavy cream until smooth.
10. Shape the Croissants: Roll out the laminated dough into a large rectangle about ¼ inch thick. Cut the dough into triangles, placing a teaspoon of the salted egg yolk mixture at the base of each triangle. Roll each triangle starting from the base to the tip.
11. Proof the Croissants: Place the shaped croissants on a lined baking sheet. Cover with plastic wrap and let them rise for about 30 minutes until slightly puffed.
12. Preheat Oven: Preheat your oven to 375°F (190°C) while the croissants are proofing.
13. Brush with Egg Wash: Once the croissants have risen, brush them with the egg wash for a golden finish.
14. Bake: Bake in the preheated oven for 20-25 minutes or until golden brown and flaky.
15. Cool: Remove from the oven and allow the croissants to cool slightly on a wire rack.

By following these steps, you’ll create an impressive batch of Charcoal-Dough Croissants with Salted Egg Yolk Lava that will surely impress!