Combine eggs, sugar, and milk in a large bowl. Whisk well. Sift in flour and cooca powder. Add salt. Mix until just combined.
Heat a small non-stick pan with butter over medium-high heat. Pour a scant ½ cup batter into pan and tilt to coat. Cook for 1 to 2 minutes until lightly browned and then flip the crepe. Cook the second side for one additional minute, until light brown. Stack the crepes on a heatsafe plate and continue making crepes until you finish the batter. Melt more butter in pan as needed. You should get about ten crepes.
On a platter or cake plate, place a crepe and spread with whipped cream. Cover with a second crepe and continue layering until you have used all the crepes.
Using a squeeze bottle or a spoon, drizzle chocolate ganache over the cake before serving.