The day before eating this dish, or the morning of, preheat oven to 400 degrees. Wash the sweet potatoes and place in a 9X13 baking dish. Add 1 cup of water, and cover with aluminum foil. Bake for 1 ½ hours or until sweet potatoes are soft to the touch.
Allow sweet potatoes to cool completely. This will take a few hours at least. You can also place the sweet potatoes in the refrigerator to cool them down faster.
When you're ready to make candied sweet potatoes, preheat your oven to 375 degrees.
Peel your sweet potatoes (they should peel very easily), and slice them in half like a hot dog. Then slice those long halves in half like a hamburger. Slice each quarter into 2 or 3 slices. You want the sweet potatoes to be in spears, not rounds.
Lay the sweet potato spears in a 9X13 baking dish. It's ok if you have to overlap the slices.
In a mixing bowl, mix together the apple juice, maple syrup, and corn starch. Whisk it until there are no lumps of corn starch. Pour the mixture over the sweet potatoes.
Top the sweet potatoes with lots of cinnamon, pumpkin pie spice, and salt.
Bake for 45 minutes. This allows the corn starch to thicken the sauce. It's so good!
As the dish cools down, the sauce will thicken even more.