Place a sweet potato on a cutting board and place 2 wooden spoons or chopsticks on both sides of the sweet potato.
Use a sharp knife to cut slices down the length of the potato that are approximately 1/8 inch thick. The wooden spoons or chopsticks will keep you from cutting all the way through the potato.
Continue this process until all the potatoes have been prepared.
Then place the potatoes on a baking sheet lined with foil or parchment paper.
Stir together the butter, oil, salt, brown sugar and cinnamon.
Brush half of this mixture onto the potatoes and in between the slices with a pastry brush.
Cover the potatoes loosely with foil and bake for 30 minutes.
Remove from the oven, uncover and brush the remaining butter mixture onto the top of the potatoes.
Bake (uncovered) for 30-35 more minutes until the potatoes are cooked through.
Remove from the oven. Serve warm and enjoy!
Notes
Refrigerate the leftovers in an airtight container for up to 5 days.