In a large mixing bowl, combine the flour, sugar, and salt.

Add the chilled butter cubes and use a pastry cutter or your fingers to mix the butter into the flour until the mixture resembles coarse crumbs.

Gradually add cold water, one tablespoon at a time, mixing until the dough comes together.

Form the dough into a ball, wrap it in plastic wrap, and refrigerate for at least 30 minutes to chill.

In a medium bowl, combine the blueberries, sugar, cornstarch, lemon zest, and lemon juice.

Stir gently to coat the blueberries evenly with the sugar and cornstarch mixture. Set aside to allow the filling to thicken.

Preheat your oven to 375°F (190°C).

Roll out the chilled dough on a lightly floured surface to about 1/8-inch thickness.

Using a round cookie cutter or a glass, cut out small circles of dough to fit into the muffin tin. Gently press the dough into each muffin cup.

Spoon the blueberry mixture into each crust, filling them generously.

If desired, top each mini pie with a lattice crust or cover with a full dough circle, pressing the edges to seal. Cut a few slits in the top for ventilation.

Brush the top of each pie with an egg wash (optional: a beaten egg mixed with a teaspoon of water) to give them a golden color when baked.

Place the muffin tin in the oven and bake for 20-25 minutes, or until the crust is golden and the blueberry filling is bubbling.

Allow the mini blueberry pies to cool in the muffin tin for about 10 minutes, then transfer them to a wire rack to cool completely.

Serve with a dollop of whipped cream or a dusting of powdered sugar, if desired. Enjoy your delicious mini blueberry pies!