Sift together first 5 ingredients in a large bowl. Chill 1 hour.
Line a baking sheet with parchment paper. Lightly coat parchment paper with cooking spray. Set aside.
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.)
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.
Stir together egg yolk and 1/4 cup buttermilk.
Brush mixture onto shortcake tops, and sprinkle evenly with coarse sugar.
Bake at 425 for 12 to 15 minutes or until lightly browned.
Remove baking sheet to wire racks to cool.
Stir together peaches, blueberries, 1/2 cup granulated sugar, and ground nutmeg; cover and chill.
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.
Split shortcakes in half. Spoon fruit mixture on bottom halves of shortcakes; top with remaining halves and a dollop of whipped cream.
