Preheat your oven to 350°F (175°C).
In a medium mixing bowl, combine the two cans of peaches (including their juices), the bourbon, cinnamon, and nutmeg. Stir gently to incorporate the spices.
Pour the peach mixture into the 9×13 inch baking dish, spreading them into an even layer.
Sprinkle the dry yellow cake mix evenly over the peaches. Do not stir the mixture; ensure the cake mix covers the fruit completely.
Place the thin slices of cold butter across the top of the cake mix, spacing them out so they cover as much surface area as possible.
If using, scatter the chopped pecans over the top of the butter.
Bake for 30 to 35 minutes, or until the top is golden brown and the fruit juices are bubbling vigorously around the edges.
Remove from the oven and allow the dessert to rest for 10 minutes before serving to let the sauce thicken slightly.