Beat the egg yolks with half of the sugar until light and fluffy. Set aside.
Whip the egg whites to a foam. Gradually add the remaining sugar and whip to soft peaks.
Combine the melted chocolate with the egg yolk mixture. Carefully fold in the egg whites and the flour. Spread the batter to a rectangle measuring 12 × 16 inches (30 × 40 cm) on a sheet o