Preheat oven to 425 degrees F. Place all ingredients, except the butter, crust and egg wash, in a large bowl. Gently toss to combine. Spoon the filling into bottom pie crust, and then dot top with butter. Brush edges of the bottom crust with egg-wash. Set on top crust, crimping the edges to seal. Brush top of pie with egg-wash. Cut a small hole in the centre of the pie to allow steam to escape. Bake 20 minutes. Reduce heat to 325 degrees F and cook 30 minutes more, or until the pears are tender when poked with a thin knife.