In a large bowl combine the flour, baking powder, baking soda, salt, and sugar then whisk together. If using a food processor then pulse the ingredients together.
Whisk together the egg, buttermilk, and cream in a bowl or liquid measuring cup and set aside.
Add the cold cubed butter to the dry mixture then work it in with your hands until you have a crumbly mixture with lentil to almond-sized pieces of butter. If using a food processor then pulse a few times until butter is broken into large crumbs.
Pour the milk mixture on top of the flour mixture and mix (or pulse) until a shaggy dough starts to form.
Dump the dough out onto a clean surface generously sprinkled with flour. Work the dough just until it holds together then pat down to an inch in thickness. Use a floured 2 ½-3 inch biscuit cutter to cut the shortcakes out. Press straight down with the cutter and don’t twist; twisting seals the edge and prevents the shortcake from rising. Push together the scraps and cut the remaining shortcakes.
Transfer to baking sheets lined with parchment paper or Silpat. Brush tops, not sides, with cream and sprinkle with sugar.
Bake at 425F for about 15 minutes or until golden and puffed up.
Remove cakes from the oven and allow them to cool.