Process first 3 ingredients in a food processor until very smooth, about 2 minutes. Add eggs, sugar, and vanilla; process until blended. Pour into a greased 13" x 9" baking dish.
Cover and bake at 350º for 15 minutes; uncover and sprinkle with marshmallows. Bake, uncovered, 20 more minutes or until marshmallows are toasted. Serve hot.
*For best results, we recommend buying and cooking 3 large, deep orange sweet potatoes. Cut them in half crosswise; boil them in their skins 35 to 37 minutes or until very tender. Cool and slip potatoes out of their skins. Mash with a potato masher to equal 3 1/2 cups. In a pinch, use 2 (29-ounce) cans candied yams as a substitute. Each (29-ounce) can yields 2 cups mashed.