Stop Losing Pie Filling Through Crust Cracks With This Simple Trick - Tasting Table

"This method is best implemented when blind baking the crust, which means cooking the crust before adding the filling. It's an important technique for certain pies, but it does mean that cracks can't form when rolling out and cooking the dough. Before adding the filling to a blind-baked pie crust, simply beat an egg white and brush it over the entire thing. The egg white will fall into any small cracks and heat up thanks to the crust already being hot, forming a seal."

"While the egg white method is a simple solution to a cracked crust after it's already been cooked, if you're making your crust from scratch, there are other methods you can employ to make sure the dough doesn't crack. For starters, be sure the fat (which typically comes in the form of butter, such as in this pie crust recipe) is thoroughly incorporated. Chunks of fat in your dough will keep everything from mixing properly and give you air pockets that turn into cracks."

Blind baking involves cooking the crust before adding the filling. Beating an egg white and brushing it over a hot blind-baked crust allows the egg white to settle into small cracks and coagulate, sealing them immediately. This technique is especially useful for custards and other liquid fillings that can leak through tiny holes. The method is less necessary for non-blind-baked crusts or pies with solid fillings. When making crust from scratch, thoroughly incorporate the fat to avoid large chunks that create air pockets; properly cut-in butter prevents air pockets that can become cracks.

Read at Tasting Table