1. Sift together first 5 ingredients in a large bowl. Chill 1 hour.
2. Line a baking sheet with parchment paper. Lightly coat parchment paper with cooking spray. Set aside.
3. Cut shortening and butter into cold flour mixture with a fork or pastry blender until crumbly. Add 2 cups cold buttermilk, stirring just until dry ingredients are moistened. (Dough will be light and crumbly.)
4. Turn dough out onto a floured surface. Pat dough into a 1-inch-thick circle, and cut with a floured 3-inch round cutter. Place shortcakes 2 inches apart on prepared baking sheet. Repeat procedure once with remaining scraps of dough.
5. Stir together egg yolk and 1/4 cup buttermilk. Brush mixture onto shortcake tops, and sprinkle evenly with coarse sugar.
6. Bake at 425° for 12 to 15 minutes or until lightly browned. Remove baking sheet to wire racks to cool.
7. Stir together peaches, blueberries, 1/2 cup granulated sugar, and ground nutmeg; cover and chill.
8. Beat 1 cup whipping cream and 3 tablespoons confectioners sugar at medium speed with an electric mixer until soft peaks form. Stir in 3 tablespoons almond liqueur, if desired.
9. Split shortcakes in half. Spoon fruit mixture on bottom halves of shortcakes; top with remaining halves and a dollop of whipped cream. Garnish, if desired.