Lemon Poppy-Seed Shortcakes with Blueberries and Cream

-Preheat oven to 400°F. Line a baking sheet with parchment paper; set aside.
-In a small saucepan, warm apricot jam over medium heat on stovetop. Add blueberries, tossing gently to coat; remove from heat. Set aside.
-In a medium bowl, combine flour, 1/2 cup sugar, lemon zest, poppy seeds, baking powder, and baking soda; stir to mix well. Using a pastry blender, cut butter into flour mixture until it resembles coarse crumbs.
-In a separate bowl, combine 1/4 cup cream, buttermilk, and vanilla. Add buttermilk mixture to flour mixture, stirring until dough is just combined. (Dough will be sticky.)
-On a lightly floured surface, roll dough into a 1-inch-thick circle. Cut with a 2-1/2 inch round cutter and place on prepared baking sheet. Brush with egg white and sprinkle with remaining 2 tablespoons sugar.
-Bake for 12 to 14 minutes, or until lightly browned. Remove to wire rack and cool completely.
-In a medium bowl, combine remaining 1 cup cream and confectioners' sugar. Beat with an electric mixer at medium speed until stiff peaks form.
-To serve, split shortcakes in half horizontally. Layer blueberries and whipped cream on bottom halves; replace tops of shortcakes.
-Garnish with a dollop of whipped cream, additional blueberries, and lemon zest, if desired.