Preheat the oven to 375 F.
Preparing the Mason Jar Lids - Clean the top and bottom of each Mason jar lid. Turn the inside of each lid over so that the metal part inside of the rim is facing up (instead of the side with the rubber seal on it). This way the pie dough will come in contact with the metal side of the lid rather than the side with the rubber on it. Set the lids aside.
Cutting the Dough - Sprinkle flour on the dough rolling surface and lay out one of the rounds of dough. The dough for the crust (top and bottom) needs to be cut 1-inch larger in diameter than the size of the Mason jar lid. If using 3-inch diameter Mason jar lids, the small dough rounds or pie crusts need to be 4-inches in diameter.
To cut the pie crusts, use a glass (with thin edges) that is 4-inches in diameter or use a Mason jar lid as a guide and cut the round 1-inch larger in diameter with a knife.
Each large round of dough should yield 8 pie crusts (small rounds); 2 of the small rounds will need to be made from the scraps after cutting 6 small rounds.
Filling the Pies - Lay a small round of dough in a Mason jar lid. With your fingers, gently push the dough evenly inside of the lid.
With a slotted spoon, spoon the berry mixture (not the juice) into the pie shells.
Or if using a regular spoon, drain the juice back into the bowl (when the berries are in the spoon, lean the spoon on the inside of the bowl to drain the juice).
Top the berries with lemon curd. Be careful not to fill the pie shells too full. Leave enough room for the top crust to cover the berries and overlap the bottom crust.
Adding the Top Layer of Pie Dough - Dip your finger in water and run it around the inside edge of the bottom pie crust.
Top the pie with a small round of dough and pinch the edges of the top and bottom crusts together so that they are tightly sealed.
Roll the edges of the pie and tuck them into the top of the lid. Repeat the process with the remaining pies.
For the Egg Wash and Sugar Topping - In a small bowl add the egg and water. Whisk the egg wash together. Brush the egg wash on top of the pies. Sprinkle sugar crystals on top of the pies.
Cut slits on top of the pies so that steam can escape.
Baking the Pies - Line a shallow baking pan or cookie sheet (with sides) with parchment paper. Put the pies on the pan leaving some space in between each pie.
Bake in a preheated oven until the pie crusts turn a golden brown (about 35 to 40 minutes). Juice from the pies may bubble outside of the pies on to the parchment paper.
Let the pies cool until the lids are cool enough to handle.
Removing the Pies from the Mason Jar Lids - Carefully push the bottoms of the lids up and out of the rim section. Then carefully remove the bottom parts of the lids from the pies.
Serve as soon as the pies are removed from the lids so they're still warm.