Preheat oven to 400°F.
Peel yams or sweet potatoes (either may be used). Cut into 1-inch cubes or wedges.

Butter a 9x13-inch baking dish generously. Arrange yams in baking dish.

In a saucepan, melt butter, and stir sugar until dissolved over medium heat. Add 1/4 cup water and spices. Bring to a boil, add maple syrup, reduce heat to a simmer and cook for 2 minutes. Pour butter mixture over the yams, turning them over to coat well. Cover the yams tightly with aluminum foil and bake on center rack in oven, basting the potatoes with the butter syrup once or twice during the baking for about 45 minutes or until fork tender.

Note: If adding mini-marshmallows, spread them evenly over the top of the potatoes at this time, and broil for 5-10 minutes or until lightly browned, otherwise proceed with next step.

When the potatoes are done, remove foil. Bake on the upper third of the oven at 475°F until the syrup has thickened and the potatoes are just beginning to caramelize (about 20 minutes - but watch carefully and do not allow them to burn, if they are browning too quickly reduce oven temperature).

Baste with additional butter before serving.