1.Have unbaked pastry dough ready - it should be refrigerated at least 20 minutes and can even be made the day before and kept chilled. (See "Make Basic Piecrust," under Related Hows.)
2.Preheat the oven to 400 degrees F.
3.Toss blueberries lightly in a bowl with sugar, flour, lemon juice and grated lemon zest.
4.Sprinkle a little more flour onto your work surface.
5.Divide the dough into two balls, one slightly larger than the other. Use a heavy rolling pin to roll out the larger ball into a circle about 1/8-inch thick and a bit larger than the pan. (See "Roll Out Dough," under Related Hows.)
6.Transfer the rolled dough to the pie pan or dish - it's easier to lift if you drape it over the rolling pin first. Fit the dough into the pan for the bottom crust, but don't stretch the dough (see Tips).
7.Trim the edges of the crust to a 1-inch overhang.
8.Turn the blueberry mixture out of the bowl into the dough-lined pan and dot it with pieces of butter.
9.Roll out the second ball of dough to about 1/8-inch thickness. Place it over the blueberry filling. Trim the edges to a 1-inch overhang.
1..Fold the top crust over the lower crust and press them together with your fingers. Crimp the edges decoratively, then cut a few vents in the top crust to let steam escape.
1..Brush egg-water mixture onto the top crust. It will form a shiny glaze as the pie bakes.
1..Bake about 35 to 45 minutes, until the pastry is golden.
Learning how to make piecrust takes practice. Keep your ingredients cold and try not to work the dough too much. Avoid stretching the dough to fill the pan; the crust will shrink as it bakes if you do.
For a variation, try brown sugar and lime with blueberries instead of white sugar and lemon.