In a large bowl, whisk together the eggs, brown sugar, and granulated sugar for 2-3 minutes until combined. There should be small bubbles in the mixture when you let it sit. With a rubber spatula, slowly stir in 1/3 of the cooled chocolate. Continue to add 1/3 at a time, stirring to combine. Sift in the dark cocoa powder, flour, and corn starch until just combined.