1Heat oven to 350°F. Place yams in a large pot (they should fit in a single layer). Cover with cold water and add salt and cloves. Bring to a boil over medium heat; cover pot and reduce heat to medium low. Simmer until yams give only a little resistance when pierced with a sharp knife, about 20 minutes. Drain yams and rinse under cold water.
2Butter an 11-by-7-inch baking dish. When yams are cool enough to handle, peel and cut into 1-inch cubes. Transfer to the baking dish and set aside.
3Melt butter in a small frying pan over low heat. Add sugar, stirring until dissolved. Stir in apple juice, drizzle mixture over yams, and bake, stirring occasionally, until yams are syrupy, bubbly, and completely cooked, about 20 minutes.
4If topping with marshmallows, heat broiler. Sprinkle marshmallows over yams and broil until lightly toasted, about 1 minute. (Watch carefully so they don’t burn.) Serve.