To prepare filling, combine first 5 ingredients in a bowl. Cover and chill 2 hours.
Preheat oven to 400°.
To prepare shortcakes, lightly spoon flour into dry measuring cups; level with a knife. Combine flour, 1/2 cup sugar, baking powder, and salt in a large bowl; stir well with a whisk. Cut in butter with a pastry blender or 2 knives until mixture resembles coarse meal. Add buttermilk; stir just until moist.
Turn dough out onto a lightly floured surface; knead lightly 4 to 5 times. Pat dough into a 9-inch round cake pan coated with cooking spray. Cut dough into 10 wedges, cutting into but not through dough. Combine water and egg white; brush mixture over dough. Sprinkle 2 teaspoons sugar over dough.
Bake at 400° for 25 minutes or until golden. Cool in pan 5 minutes on a wire rack; remove from pan. Cool completely on wire rack. Cut shortcake into 10 wedges. Split each wedge in half horizontally. Fill each wedge with 1/2 cup filling.
This shortcake was the best we have ever eaten! The buttermilk added a subtle flavor and lightness that eliminated the doughy consistency of most shortcake recipes. I was skeptical of adding the orange sections to the fruit but it really played well with the buttermilk in the cake and contrasted well the strawberries and berries. Everyone LOVED it!
Sign Up for our Newsletter
Join our newsletter for free recipes, healthy living inspiration, and special offers.