Sweet Potato Bake with Apples and Parmesan

I have a confession: this recipe was a flop but still tastes delicious so I went ahead and put it on my blog anyway.  I was originally trying to make little cannelloni with sweet potatoes but I sliced them with the mandoline too thick so they wouldn't roll up (they kept breaking).  I was planning on stuffing them with mashed sweet potato mixed with apples and parmesan, but instead I layered the whole dish into a casserole pan and threw it in the oven.  It doesn't look as pretty as I originally intended but it still tastes delicious.  I got the idea of sweet potato cantollini from a Martha Stewart magazine and I will share the original recipe here in case you are brave enough to try it.

Sometimes a mistake is still delicious enough to eat and share!

Ingredients:
3 large sweet potatoes, peeled
1 sweet-crisp apple, diced (Honey Crisp or Fuji would be nice)
1/2c parmesan cheese, shredded, plus more for serving
1/2tsp sea salt
Freshly ground pepper
4tbs butter
1/2c chopped walnuts, toasted

Directions:
1. Preheat oven to 350.  Bring a large stock pot filled with water to a boil.
2. While you are waiting, use a mandoline to cut very thin long slices on each potato (keep the mess-ups, they get boiled first).  You want about 32 pieces that are about 2x4".  The small and extra pieces, throw in the boiling water until very soft (5 minutes).  Remove and put them in a food processor until smooth.  Add parmesan cheese, a bit of salt, and your diced apple and stir.  Set aside.
3. With your cannelloni slices, place them in the boiling water until soft (2 minutes).  Remove gently and let cool slightly on a baking pan.
4. Spray the bottom of a casserole dish with cooking spray.  Add a heaping tablespoon of potato apple mix to the center of a sweet potato slice and roll up.  Place seam side down.  Repeat.  (If you mess up like I do, don't let it go to waste!  I put a layer of potato slices on the bottom, followed by the sweet potato apple mash, and topped with the potato layers again.)
5. When you are done, brush the entire dish generously with butter and sprinkle with remaining sea salt.  Bake in the oven about 20 minutes or until everything is hot.  Top with more parmesan and toasted walnuts.