Add eggs, cold water, cold milk, flour, unsweetened cocoa powder, granulated sugar, salt, and vanilla to a blender and blend until smooth.
Add the butter and blend again for a few seconds. Rest the batter for at least 15 minutes.
While the batter is resting, preheat your crepe pan (or any 10 inch pan) on medium heat.
Once the batter has rested, pour ⅓ cup of the batter into the pan and swirl.
Cook for about 1 minute on medium heat until the surface of the crepe looks dry, then flip and cook for another 15-30 seconds, then transfer to a plate.
Repeat with remaining batter, stacking the crepes on top of each other.
Fill with your favorite toppings like whipped cream and Nutella and serve immediately.
