Here's a beautiful and delicious alternative to candied yams and heavy sweet potato casseroles - the apples lend a bit of tart sweetness and ginger snap crumbs spice things up a bit.
1 pound Granny Smith apples, peeled, cored, and cut 1/3" thick
2 1/2 pounds sweet potatoes, peeled and cut 1/3" thick
1 1/4 cup heavy cream
1 cup whole milk
1 teaspoon lemon juice
1/3 cup maple syrup
1 tablespoon arrowroot powder
1 tablespoon unsalted butter
1 1/2" piece fresh ginger, peeled
2 cinnamon sticks
Pinch fresh ground nutmeg
1/3 cup ginger snaps, crushed
1. Heat the cream and milk over low heat until warm. Add the cinnamon sticks, ginger, and nutmeg. Remove from the heat and allow to steep at room temperature for 1 - 3 hours.
2. Mix 1/3 of the milk with the arrowroot powder until well combined to make a slurry.
3. Remove the cinnamon stick and ginger from the spiced milk and discard. Combine the spiced milk with the slurry.
4. Preheat oven to 375 degrees.
5. Well butter a 9 x 13" casserole dish. Create one layer of the sliced sweet potatoes, slightly overlapping. Drizzle with about one tablespoon of the maple syrup.
6. Add a layer of the apples in the same fashion as the sweet potatoes. Sprinkle with the lemon juice and drizzle with another tablespoon of maple syrup.
7. Add another layer of the sweet potatoes and drizzle with the remaining maple syrup. Pour the milk and cream mixture evenly over the potatoes and apples. Cover tightly with foil and bake for 40 minutes.
8. Remove the casserole dish from the oven and remove the foil. Raise over temperature to 375 degrees. Evenly sprinkle the crushed gingersnaps over the gratin. Return the casserole dish to the oven and bake uncovered for another 20 minutes.
9. Remove from the oven and let cool for 20 minutes before serving.