Whisk flour, cocoa powder, sugar, and salt in a large bowl. In another bowl, beat eggs with milk, melted butter, and vanilla until smooth. Gradually pour the wet ingredients into the dry ingredients, whisking constantly to prevent lumps. The batter should be thin and pourable, like heavy cream. Let it rest for 5 minutes while your pan heats up.

Use a non-stick 8-inch skillet or traditional crepe pan over medium heat. Lightly butter the surface. The pan is ready when a drop of water sizzles and evaporates immediately.

Pour ¼ cup batter into the center of the hot pan, immediately tilting and swirling to spread the batter evenly across the bottom. Work quickly as the batter sets fast. Cook for 60-90 seconds until the edges look set and slightly crispy.

Using a thin spatula, carefully lift one edge and flip the crepe. The second side cooks much faster, about 30-45 seconds. Stack finished crepes on a plate, covering with a clean kitchen towel to keep warm while you finish the batch.