Good, ripe, and room-temperature peaches are the key to this recipe (or substitute nectarines). Make sure the peaches are ripe and a little soft to the touch, but not too ripe. If you buy them when they are hard, ripen them for a 2 to 3 days in a brown paper bag (throw in a banana for extra power). Five average sized peaches are usually enough for the recipe, but buying one or two extra is good insurance in case a peach goes bad. Another key to great peach pie is refrigerating it after baking to thicken the custard.