Preheat oven to 350 degrees F. Butter 2 9-inch round cake pans then line bottom with a round of parchment paper. Butter parchment then dust pans lightly with cocoa powder or flour and shake out excess. Set aside.
In a large mixing bowl whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt.
For the frosting: in a large saucepan whisk together egg yolks and evaporated milk until very well combined.