Special equipment: 12-cup muffin tin
Preheat oven to 400 degrees. Slice the sweet potato into thin rounds. Put one slice of the sweet potato into each cup of a 12-cup muffin tin. Top with a pinch each of the shredded gruyere, the diced pancetta, salt and white pepper. Top with another slice of sweet potato, and continue to layer as described above until the muffin cups are close to filled. Pour two tablespoons of heavy cream on top of each cup and cover loosely with aluminum foil. Bake at 400 for 15 minutes. Remove the foil and bake, uncovered, for an additional 20 minutes. Allow to cool before removing from muffin tin and serve as a side dish to your favorite main course.
Yield: 12 individual gratins