Cut any kind of bread into 1-inch cubes - I recommend a crusty, whole grain variety, but sandwich bread will work, too. Just use enough slice to fill a lightly greased 9x13-inch baking dish quite full.
In a large bowl, whisk together eggs, milk, vanilla, pumpkin butter and pie spice until well combined. Pour over bread and push down with a spoon or your hands until it's all soaked and mostly covered. Cover with saran wrap or lid and refrigerate overnight.
In the morning, preheat oven to 350 degrees F (176 C), uncover and top with brown sugar, additional pumpkin pie spice and nuts (optional). Bake for 35-45 minutes or until golden brown and no longer wet.
Serve immediately with maple syrup, honey or agave nectar. Store leftovers in the refrigerator covered for up to a couple days.
