preheat the oven to 400 (204 C) degrees
Line a 13 x 17 inch pan with parchment paper
Combine the milk, butter and vanilla in a small pan and heat just enough to melt the butter, set aside
In a stand mixer, whip the eggs, egg yolks, and sugar on high speed for 5-7 minutes or until it forms wide bands of ribbons when the beater is lifted out.
Gently transfer the egg mixture to a bowl large enough to make folding in the other ingredients easy.
Pour in the butter/milk mixture down the side of the bowl and fold this into the egg mixture using a rubber spatula.
Sift the flour over the egg mixture, doing this in three batches. After sifting, gently begin to fold the flour into the mixture. (the flour will settle on the bottom, fold more than you think you should, I still wound up with little flour balls in my cake)
Continue sifting in the flour in the three batches until it has all been folded in. (don't forget to check the bottom of the bowl for more flour)
Pour the mixture into the lined sheet pan and using an offset spatula smooth out the mixture evenly. Use your finger to run down the insides of the pan creating a momentary separation of the cake from the pan.
Place on center rack in the oven and bake for 12 minutes.
Allow the cake to cool for 10 minutes, then turn the cake out onto a clean piece of parchment that has been dusted with 10x sugar. (do this quickly so it does not tear)
Gently peal off the parchment from the bottom of the cake (use a metal spatula if it is hard to remove)