Made with an all butter crust, this apple slab pie is ultra flaky and tender and feels really fancy but uses only simple ingredients. Perfect to feed LOTS of people and no forks needed, you'll get all the compliments.
In a large bowl, mix the flour, salt, and 1 1/2 tablespoons sugar.
Cut the butter into small cubes with a knife and add it to the flour mixture. With a pastry blender, two knives, or your fingers, break the butter down until it's the size of small peas in the flour.
Add the water and stir to combine. Knead it around in the bowl a time or two and then divide it in to two pieces.
Wrap each piece in plastic wrap and chill in the fridge for at least 30 minutes or up to three days.
Preheat the oven to 375 and lightly grease a 10x15" rimmed jellyroll pan. Set aside.
While the dough chills, peel, core and dice the apples in to very small pieces--about 1/4". Add them to a large bowl and toss in the sugar, cornstarch and cinnamon. Set aside.
Working with one half of the dough: On a floured surface roll half the dough to a size about an inch larger than your baking pan.You can set your pan on it to see if it's big enough. Roll the dough up around your rolling pin and then unroll it over the pan, starting at one end. Adjust it with your hands to get it in straight.
Add the apples in an even layer to the pan.
Roll out the second dough in the same way and cover the top of the pie. Fold in the edges all the way around use a knife to make some holes in the top for steam to vent. Brush all over with the egg and water mixture.
Bake 45 minutes until puffed and golden. Serve warm or allow to sit at room temperature for three days.
Dough needs to chill for at least 30 minutes before rolling.