2In a medium bowl, whip egg yolks and 1/4 cup of sugar with an electric mixer until thick and pale. In a separate bowl, whip egg whites (with clean beaters) to soft peaks. Gradually sprinkle in the remaining 1/2 cup sugar while whipping to medium stiff peaks. Fold the egg yolk mixture into the egg whites. Gently fold in the flour and 1 teaspoon vanilla. The batter should be thick and pale yellow.