In a large bowl, stir the flour and oil until the mixture resembles coarse crumbs.
Cut the butter into thin slices and toss in the flour mixture to coat.
Add the ice water 1 tbsp at a time, mixing it in just until the mixture can hold its shape.
Transfer the dough onto a large sheet of saran wrap, and gather the dough tightly into a disc shape.
Divide the dough into 2 equal portions, and wrap and chill the dough in the refrigerator for 1 hour.
Next lightly flour the work surface, rolling pin, and chilled dough.
Roll one portion out to a 1/4 inch thickness, then fold it into thirds three times. Repeat this for the second portion as well.
Refrigerate both portions of dough for 1 more hour.
Unwrap one portion and roll it out to about 2 inches larger than the diameter of your pie pan.
Transfer the rolled-out dough to the pie plate and prick the bottom with a fork.
Trim off any excess dough, the fold edges under, and crimp it.
Refrigerate this dough while preparing the filling.
Filling:
Preheat oven to 450 F.
Combine sugar, flour, cinnamon, lemon zest, and juice in a mixing bowl.
Add the pears and toss to coat.
Remove the pie pan holding the dough from the refrigerator, and transfer the pear filling into it.
Arrange the slices so there are no gaps, and dot them with butter.
Roll out the second portion of dough to about 2 inches larger than the diameter of your pie pan. Cover the pie with this second portion of dough and press all around the edges to seal.
Trim off any excess dough, and crimp the edges decoratively.
In a bowl mix the milk, sugar, and butter and brush this glaze over the pie.
Make 5 evenly spaced slits in the top crust and bake the pie for 10 minutes. Reduce oven temperature to 350 F and bake until crust is golden brown and filling is bubbly (for about 35 to 40 minutes).