For shortcakes, stir together flour, the 2 tablespoons sugar, and baking powder in a medium mixing bowl. Cut in butter with a pastry blender until the mixture resembles coarse crumbs. Make a well in the center of the dry mixture; set aside.
Stir together the egg; half-and-half, light cream, or milk; and lemon peel in a small mixing bowl. Add egg mixture all at once to the dry mixture; stir just until moistened.
Turn the dough out onto a lightly floured surface. Gently knead for 10 to 12 strokes or until dough is nearly smooth. Pat dough into a 6-inch square. Cut the square into nine 2-inch squares with a floured knife; cut each square diagonally in half.
Place triangles on an ungreased baking sheet. Brush the tops with beaten egg white; lightly sprinkle with coarse sugar or granulated sugar. Bake in a 450 degree F oven for 8 to 10 minutes or until golden. Remove the shortcake triangles from the baking sheet and cool on wire racks.
Meanwhile, for topping, toss together strawberries, raspberries, the 1/3 cup sugar, Grand Marnier or orange juice, and the 4 teaspoons snipped mint in large mixing bowl. Cover and chill for up to 1 hour.
For each serving, spoon berry mixture onto a dessert plate. Place three shortcake triangles on berry mixture. Top with whipped cream and garnish with additional mint, if desired. Makes 6 servings.