On a generously floured surface, roll the disc of pie dough into a large rectangle, about 11x15in. Line a quarter sheet pan (9 1/2″ x 13″ or 24 x 33cm) with the dough. Tuck edges under, crimp, then chill the pie for at least 1 hour. May be prepared 1 day in advance.
Combine pecans, brown sugar, cornmeal, flour and cinnamon in a food processor. Pulse for about 15 seconds or until nuts are chopped. Add butter cubes and process until small clumps form, about 20 seconds. Transfer streusel to a bowl, cover and refrigerate. May be prepared 1 day in advance.
Preheat oven to 375F. Slice peaches in half around the pit, twist and open. Discard the pit. Cut peaches halves into ½ inch slices.
In a large bowl, stir together sugar, flour, salt and cinnamon. Add the sliced peaches and toss with a spatula until thoroughly coated. Add bourbon, if using and combine well.
Transfer pie filling to prepared slab pie crust and level the fruit evenly. Sprinkle on the streusel topping. Place on the bottom rack of the oven.
Bake pie until the crust and streusel are golden, about 1 hour. Cool completely before cutting and serving.
Be sure to let this pie go for the whole hour bake. Watch for bubbling in the center - this is a good sign and means those peaches are cooking down and the filling is thickening. For clean slices, let pie cool completely before cutting and serving.