
In a mixing bowl, stir together flour and salt. Toss the cold butter in the flour. Use a dough blender or your fingers to press the butter into pea-sized pieces until you have a coarse flour mixture.
Make a well in the middle of the flour. Pour ice cold water into the well. Mix until it forms a shaggy dough.
Turn the dough out onto plastic wrap, press it together, and fold it onto itself until it holds. Don't overwork.
Cut the dough into two portions, form into discs, wrap in plastic wrap, and chill for at least 2 hours or overnight.
Roll out the first disc to 1/8" thick, then place it in a 10" pie dish.
In a bowl, combine apples, cherries, brown sugar, cornstarch, cinnamon, and vanilla extract. Toss to coat.
Fill the pie with the mixture to form a dome.
Roll out the second disc, cut into strips, and create a lattice on top of the filling.
Crimp the edges and preheat the oven to 425°F.
Brush with egg wash, sprinkle with sugar, then bake for 15 minutes at 425°F followed by 50-55 minutes at 350°F.
Let cool for 1-2 hours before serving.