Preheat oven to 400 degrees. In a medium bowl, combine the cream cheese, 1/2 cup of sugar, lemon zest, and egg and stir until smooth.
In a large bowl, toss the blueberries with 1/4 cup of sugar, lemon juice, and flour. Place one pie crust on a baking sheet lined with parchment and cut into quarters with a sharp knife. Spoon 1 tablespoon of the cream cheese mixture into the center of each quarter. Then spoon 2 tablespoons of the blueberry mixture on top. Brush the edges with heavy cream and fold the crust over to create triangles.
Crimp edges of the pies to seal. Brush tops of pies with more heavy cream and sprinkle with 1/2 tablespoon of sugar. Repeat with second pie crust and fillings.
Cut a small vent in the top of each pie with a sharp knife and bake until golden, 20 -25 minutes, rotating the baking sheets in the oven halfway through.
Let the pies cool completely on wire racks before serving.
Notes
You'll have more blueberries and cream cheese than you need for this recipe, so you may want to grab a second package of pie crusts to make more pies. You could probably get another 8 servings out of it!