Wash and scrub all sweet potatoes very well and wipe dry. Slice into rounds, a little thinner than 1/4 inch (1/2 centimeter).

Preheat oven to 400 degrees Fahrenheit (200 degrees Celsius).

Place the rest of the ingredients into an extra-large ziplock bag; shake to combine. Add the potatoes to the bag and seal firmly. Shake to coat potatoes well with sauce.

Spray two nine-inch (23-centimeter) round pans

with cooking spray. Starting from the outer edge of the pan, layer the sweet potato slices, overlapping about 3/4 of the way and alternating colors every two to three slices. Continue with another circle inside that one and repeat with remaining slices

in the second pan. Stick the extra slices behind or between some others; there will be room for all potato slices.

Pour the remaining sauce from the bag over both pans and cover tightly with foil. Bake for one hour and 15 minutes. Remove from oven and uncover.

Return the pans to the oven and bake for an additional 20 minutes. Then broil for a few minutes to crisp up the edges. Serve warm, drizzled with maple syrup, if desired.