For an extra burst of flavor, add a teaspoon of lemon zest to the berry mixture. If you don't have marshmallow creme, you can substitute with an equal amount of whipped topping or heavy cream. Feel free to experiment with other berries, such as raspberries or blackberries. To prevent the shortcake from becoming soggy, serve it shortly after assembling. Or consider serving the cake and fruit separately so people can assemble their own plate.