Preheat oven to 375 degrees.

Place a yam half cut-side down on a cutting board. Lay chopsticks or thin wooden spoon handles on either side (lengthwise) of the yam. Make cuts (crosswise) about ⅛ inch apart , but don't cut all the way through. The chopsticks will prevent you from slicing straight through.

Repeat with remaining yam halves.

Combine the remaining ingredients in a bowl and divide into six equal portions.

Lay yam halves flat side down in a baking dish coated with cooking spray and top each half with a portion of the compound butter. Cover the dish with foil.

Roast for 40 mins, basting the yams occasionally. Uncover and roast for another 10 - 15 mins or until the yams are caramelized and can be easily pierced with a fork.

Switch the oven to the broil setting and scatter the marshmallows over the yams.

Broil until marshmallows are golden brown. Serve immediately.