Preheat your oven to 425°F (220°C) and prepare the muffin tin.

Roll out pie crusts to 1/8-inch thickness, cut out 12 circles, and fit them into muffin cavities.

Combine blueberries, granulated sugar, lemon zest, lemon juice, cornstarch, and a pinch of salt in a mixing bowl.

Spoon 3 tablespoons of blueberry filling into each pie crust.

Cut shapes or circles from remaining dough for tops and place them over filling, cutting slits for vents.

Brush tops with beaten egg and sprinkle with sparkling sugar.

Bake in preheated oven for 18 to 23 minutes until golden.

Cool pies in the tin for 10-15 minutes, then transfer to a wire rack.