1. Preheat oven to 375°. Layer half of sweet potatoes in a lightly greased 12-cup muffin pan. Sprinkle with 1 1/2 tsp. thyme and 1/2 cup cheese. Top with remaining sweet potatoes. (Potatoes will come slightly above the rim of each cup.)
2. Microwave cream, next 3 ingredients, and remaining 1/2 tsp. thyme at HIGH 1 minute. Pour cream mixture into muffin cups (about 1 Tbsp. per cup).
3. Bake at 375°, covered with aluminum foil, 30 minutes. Uncover and sprinkle with remaining 1/2 cup cheese. Bake 5 to 7 minutes or until cheese is melted and slightly golden.
4. Let stand 5 minutes. Run a sharp knife around rim of each cup, and lift potato stacks from cups using a spoon or thin spatula. Transfer to a serving platter. Garnish, if desired.
*Gruyère cheese may be substituted.