Toss cherries well again and spoon into shell that has been refrigerated, leaving most of the juices behind in the bowl to discard—or drink if no one is looking. (You don’t want to pour the cherries straight from the bowl or you’ll end up with a soupy pie and soggy bottom crust.) Dot the top of the cherry filling with the butter, if using. Cover with top crust pastry round. At this point, tear or cut off any overhang beyond about 1/2 an inch or so. Press or fold edges to seal, and crimp decoratively. Brush top of pie with milk or beaten egg, cut steam vents, and sprinkle crust with course sugar.