Frozen Mixed Berry Pie

Yields standard 9-inch pie (8 servings)

Preheat oven to 350 degrees Fahrenheit.
Prepare pie crust. Divide dough in half. Roll one half into a circle and fill a standard 9-inch pie plate. Cut off edges and discard.
Whisk together the sugar and cornstarch in a large bowl. Measure frozen berries into bowl as accurately as possible. (Level cups, not heaping. Or measure by weight.) Add the lemon juice. Fold together until all fruit is coated. [NOTE: Too many berries will create extra liquid that may spill over while baking, and may result in a loose, rather than thickened, filling.]
Empty berries into the prepared pie crust, distributing the cornstarch-sugar mixture as evenly as possible. (Optional: Let berries macerate for 5-10 minutes to release some juices and dissolve some of the cornstarch-sugar mixture.)
Roll the other half of the pie dough out. Cut strips for a lattice top or leave whole. Brush egg wash on the edges of the pie crust and attach the top crust to the bottom crust. Cut off any excess dough and crimp edges, if desired. Cut slits into the center of the crust if it's whole, not latticed.
Brush the top of the pie crust with egg wash and sprinkle with extra sugar.
Bake at 350˚F for 1 hr and 15 min or until the crust on top is nice and golden brown and the filling is bubbling in the center. Cover with foil if crust browns before filling bubbles. (TIP: Place a tray covered in foil on the rack underneath the pie to catch any possible spills.)