Directions

1. 1. Preheat oven to 350F. Grease and flour a 13 by 9 by 2 inch baking pan.
2. 2. Sift flour with baking powder, reserve.
3. 3. In a large bowl with clean beaters, beat egg whites and cream of tartar until frothy. Add sugar gradually, beating to form stiff peaks, reserve.
4. 4. In a separate mixing bowl cream the egg yolks and sugar; slowly add the flour and milk. Fold the egg white into the mixture until just combined. Transfer the batter into the prepared pan.
5. 5. Bake for 40 to 45 minutes or until edges are golden brown. Remove from oven and let cool on a wire rack.
6. 6. Prepare the filling by combining the three milks and sour cream, stir just to incorporate; do not beat.
7. 7. Pierce the top of the cake repeatedly with a fork. Pour the filling evenly over the cake and let it stand until all of the mixture is absorbed, 20 to 30 minutes.
8. 8. To make the meringue: Combine the sugar and water in a saucepan. Bring to a boil, stirring constantly; remove from heat and let cool. Sugar should be completely dissolved.
9. 9. In a clean electric mixer bowl with clean beaters, add the cream of tartar to the egg whites and beat them until they start to stiffen. Slowly pour the simple syrup into the egg whites, beating constantly until meringue holds stiff peaks.
10. 10. Spread the meringue over the cake and garnish with fresh berries and mint leaves.
11. 11. Store the cake in the refrigerator when not being served.