1. Preheat oven to 400º. Wash and scrub potatoes, and wrap individually in foil while still slightly damp. Place potatoes directly on oven rack; bake at 400º for about 1 hour or until tender. Remove from oven; allow to cool slightly before removing foil.
2. Cut a 3-inch slit in top of each potato, and push together at both ends. Add about 1 teaspoon butter to each, and press down into flesh of potatoes. Add sea salt and pepper; top each with 5 to 6 miniature marshmallows. Place on a baking sheet, and bake at 400° for 5 to 8 minutes or until marshmallows are golden brown and slightly melted. Serve warm with additional butter, if desired.