Preheat the oven to 325.
Prepare the graham cracker crust by crumbling up ~24 graham crackers to give 2 cups. Add 1 stick of melted butter to the crumbs and mix well with a fork until all the crumbs have absorbed the butter. If it seems to dry and not wanting to stick, add a little more melted butter.
From the crust at the bottom of a 9x13 casserole dish by pressing the mixture down with a fork. Bake for about 10 minutes or until crust seems to have set.
While the crust is baking, prepare the pumpkin and sweet potato mixture. Empty the can of yams into a large mixing bowl. Make sure the can is fully drained. With a masher, mash the yams until they are completely mashed into a puree.
To the sweet potato puree, add the pumpkin puree, eggs, pumpkin pie spice, evaporated milk, and condensed milk. Mix well.
Add this mixture to the casserole dish once the pie crust is baked. Top with the mini marshmallows and cover with aluminum foil.
Preheat the oven to 425 from the 325 when making the graham crust.
Place the pumpkin & sweet potato casserole into the oven, and reduce heat to 375. Continue to bake for 50 minutes, or until the pumpkin & sweet potato mixture is set.
Remove foil, and cook for another 5 minutes to toast the marshmallows.
Remove casserole from the oven and allow to cool for 30 minutes to finish setting. Enjoy!
