Preheat oven to 400
Stir in a bowl, melted butter, olive oil, and seasoning of choice.
Peel and thinly slice the sweet potatoes in 1/8" rounds. This is a great time to use your mandolin. Place the potatoes in the bowl with melted butter mixture and toss to coat.
Spray a muffin pan with non-stick spray and then stack the sweet potato rounds into each compartment until they are level with the top.
Drizzle any remaining butter mixture equally over each stack.
Bake at 400 for 30 to 40 minutes until done. Remove carefully and serve upside down. Top with flaky salt if desired.