In a large bowl combine the berries, 3/4 cup of the sugar, water, and 1 teaspoon of the orange zest in a large bowl. Stir well to combine. Cover with plastic wrap and refrigerate until the berries have softened and given up their juices and mixture is chilled, about 1 hour.
Position rack in center of oven and preheat the oven to 475 degrees F.
Sift the self-rising flour, cake flour, 1 tablespoon of the sugar, baking powder, salt, and baking soda into a medium mixing bowl. Add the butter and remaining orange zest to the flour mixture and, using your fingers or a pastry cutter, work the cold butter into the flour until there are no butter pieces larger than a pea. Add the heavy cream to the flour mixture and, using your hands or a rubber spatula, stir just until the cream and flour come together to form a dough. Do not overmix!
Sprinkle some of the all-purpose flour on a flat surface and place the dough on top of the flour. Using your hands, press the dough into a 1/2-inch thick disk about 8 inches in diameter.
Using a 3-inch round cutter dipped in flour, cut the dough into circles. Be sure to press straight downward when cutting the dough a twisting motion will prevent the dough from rising. You will need to re-form the scraps of dough in order to make 8 shortcakes. Do this by gathering the scrap pieces together and pressing to re-form into a 1/2-inch thick disk, then cut as many additional shortcakes as possible from the re-formed dough.
Place the shortcakes on a small baking sheet and use a pastry brush to brush the tops with the melted butter. Sprinkle the tops of the shortcakes with the remaining tablespoon of sugar and bake in the oven for 10 to 12 minutes, or until golden brown.
Remove the shortcakes from the oven and transfer to a wire rack to cool. The shortcakes can be served warm or at room temperature.
To assemble the shortcakes: Using a knife or fork, split the shortcakes in half horizontally and place the bottom halves on each of 8 plates.
Divide the berries evenly among the bottom halves and top each serving with a dollop of whipped cream. Lean a shortcake top against each bottom and serve, garnished with a sprig of mint.