Pre heat oven to 350F (180C). Grease and flour an 8" or 9" pie plate (20-23 cm)
FOR THE PIE CRUST
In a medium bowl whisk together the flour (start with 1 3/4 cups) sugar and baking powder, cut in the butter with a pastry blender until it resembles coarse crumbs, then add the egg and egg yolk, bring it together slightly with a fork. If dough is too wet then add extra flour, one tablespoon at a time.
Turn onto a lightly floured surface, work the dough together to form a soft dough (if too sticky add a little more flour). Wrap in plastic and refrigerate for at least 30 minutes.
Remove from fridge and knead a few times to soften up the dough, if needed. Divide the dough into 2 equal parts, and roll with a lightly floured rolling pin into two circles. Fit the dough into the prepared pie plate with the dough.
FOR THE APPLE FILLING
Meanwhile, while the dough chills in the fridge start to prepare the filling. In a medium-large sized pot add the butter and melt over low heat, then add the brown sugar, apples and cinnamon, stir to combine and continue to cook on low / medium heat for approximately 10-15 minutes, stirring often, then add the cornstarch, stir to combine and continue to cook for approximately 3-5 minutes until thickened (will still be a little runny), remove from heat.
Pour the filling on the pie crust and top with the second pie dough*. Bake for approximately 30 minutes. Check after 20 minutes and if crust is browning too much then cover with foil and continue baking. Enjoy!
*You can cover with strips, or use a small cookie cutter to make different forms.