Preheat oven to 400°F
Peel and core apples. Slice them into a large bowl. Stir in sugar, cinnamon and cornstarch.
Roll out bottom crust (aim to roll dough to about an 1/8” thickness) and place in 9” pie plate. Trim the dough so that it overhangs the pie plate by about 1/2". Gently pour prepared apples into the pie crust and scatter butter pieces evenly over the top.
Roll out top crust and gently transfer to top of pie. Trim overhanging edges to about 1-1 ¼ inches all the way around. As best you can, fold the top overhanging crust around and under the lower crust and onto the pie plate rim. Crimp edges to seal pie by fluting with fingers.
If desired, brush whisked egg white over the crust.
Place in 400°F oven for 15 minutes (either with a baking sheet directly underneath it or on the rack below to catch any sugary drippings).
Turn oven temperature down to 350°F and continue baking for 45-55 minutes longer until juices are bubbling and apples are tender. Check pie occasionally throughout baking to ensure crust is not burning. If it is trending towards too brown (or burnt!) gently cover with aluminum foil.
Allow pie to cool for a few hours before serving!