Preheat oven to 350°
Arrange the sliced sweet potatoes in a 9x13 baking dish.
Place the butter into a small pot, then melt it over medium heat. Once the butter is melted, sprinkle in the white & brown sugar, ground cinnamon, ground nutmeg, ground ginger, ground clove and vanilla extract.
Continue to stir the ingredients together over medium heat, allowing them to combine for about 6-7 minutes, then remove from heat.
Pour the mixture over the sliced sweet potatoes, coating each of them.
Cover the baking dish with foil, then place in the oven for 45 minutes.
After 45 minutes, remove the baking dish from the oven and baste them with the candied mixture, spooning it over the top of the candied yams. Place the foil back over the baking dish and put it back in the oven for 30-45 minutes more or until the sweet potatoes are tender. Once the sweet potatoes are tender, add vegan marshmallows overtop (if desired) and continue baking until lightly browned.
Once done, remove from the oven and let cool for 10 minutes or so. Enjoy!