In a large bowl, mix together the blueberries, sugar, flour, cinnamon and water. When stirring, break up a few of the berries to release some juice. Allow to sit for 15-20 minutes.
Preheat your oven to 350 degrees F.
On a lightly floured surface, unroll your pie dough. Using a rolling pin, roll out the dough to increase its size by 15%. Next, cut three circles out of one of the pieces of pie dough and another circle out of the second piece of dough. Each dough circle should be about 1 1/2 inches larger than the rim of your mason jar. With the remaining dough, use a star cookie cutter to cut out four stars. These stars will be the tops for your pies.
Place a cut dough circle into each mason jar, being careful not to stretch the dough.
Next, evenly divide the blueberry mixture among the dough-lined mason jars. Place a star cut from the dough on top of each pie. Trim off any access dough from the rim.
Lightly brush the dough with the egg wash and sprinkle with coarse sugar. Place the mason jars on a cookie sheet for baking.
Bake for 30-35 minutes or until the crust is golden and the filling is bubbly.