Sweet Potato Stacks

My mother-in-law makes a fabulous Sweet Potato Souffle. It's so good, and so NOT good for you. I've spent a lot of time trying to come up with a recipe that captures the flavor yet doesn't have quite so many calories. Her casserole calls for a delicious smorgasbord of butter, eggs, pecans, and brown sugar, and it's hard to re-create the taste while taking out those ingredients.

The best I've come up with is Sweet Potato Stacks:

2 small sweet potatoes, peeled and thinly sliced (as thin as you can manage!)
1 small apple, cored, peeled and thinly sliced (preferably a sweet but firm one like Gala or Honeycrisp)
3/4 cup apple juice or orange juice
1/3 cup butter (approximately)
1/2 cup quick-cooking oats
1 teaspoon cinnamon
1/4 cup brown sugar

In a small bowl, combine the oats, cinnamon and sugar. In each of 12 muffin cups, place about a tablespoon of juice. Layer with a couple of slices of sweet potato, a couple of slices of apple, about 2 teaspoons of the oat mixture, more sweet potato (to top off cup), more oat mixture, and a half-tablespoon of butter. Bake at 350 for 20-25 minutes or until potatoes are tender when pierced with a knife. You will need to remove the stacks from the cups while still hot, or they'll stick to the pan.