In a blender, combine the all-purpose flour, unsweetened cocoa powder, granulated sugar, and kosher salt. Add the eggs, whole milk, melted unsalted butter, and vanilla extract. Blend until smooth, about 30 seconds. Let the batter rest for 15 minutes.

Preheat a 10-inch nonstick skillet over medium heat for about 2-3 minutes, lightly brush the surface with melted butter.

Pour 1/4 cup of the rested batter into the center of the skillet, swirl the pan to coat the bottom evenly. Cook for 1-1.5 minutes until edges lift. Flip and cook for 30-45 seconds.

Transfer the cooked crepes to a plate, stacking them and covering with a clean kitchen towel to maintain warmth.