Heat oven to 375°F/190℃.
Line a sheet pan with parchment paper. Set aside.
In a small bowl, whisk together cream and egg. Set aside.
In a large bowl, whisk together flour, sugar, baking powder, baking soda, salt, and lemon zest.
Cut in shortening with a pastry blender to the size of small peas.
Pour liquid ingredients over dry ingredients.
Stir just until combined.
Fold in blueberries.
Roll out into 9-inch x 12-inch rectangle.
Cut into 12 squares.
Place on prepared baking sheets.
Freeze for 20 minutes.
Brush tops with cream.
Sprinkle with sparkling sugar.
Bake until golden brown, 20-25 minutes.