1. Preheat oven to 350 degree F.
2. Peel yam and cut it lengthwise into half.
3. Grease a large baking pan with ½ tablespoon vegetable oil.
4. In baking pan place yam, sprinkle remaining vegetable oil on top, and mix to coat it well.
5. Season with salt and pepper.
6. Arrange yam pieces on baking pan, with flat side up.
7. Place baking pan in oven, and roast for about 40-45 minutes or until fork tender.
8. Remove the pan from oven, and dot with butter.
9. Pour maple syrup, and sprinkle brown sugar evenly on top of yam pieces. Place pan back into the oven, and roast for 10 minutes.
10. Take the pan out, baste yam pieces with the liquid in the pan.
11. Sprinkle marshmallows on top and return it back to the oven. Cook for another 8 minutes or until marshmallows melt and brown.
12. Serve candied yam with roasted turkey.
You can use big or small marshmallow. If using bigger ones cut them into smaller pieces.