About 15 minutes before the potatoes have finished, finely chop the shallot. In a medium saute pan over medium-high, heat 1 tablespoon of olive oil. Add the shallot and saute until soft, about 4 minutes. Add the kale, and saute for a few minutes, stirring constantly, until tender. Set aside.
When the potatoes have finished baking, remove them from the oven and let them cool until easy to touch. Leave the oven on. Cut the potatoes down the middle and scoop out about half of the flesh from each, making sure to keep a thick layer of sweet potato within the skin so that it can stand on its own.
In a bowl, mash the sweet potato, the roasted garlic and sage mixture and the fontina cheese. Season with salt and pepper. Divide the filling between each potato, spooning it into the shell of each.
Top with your choice of shredded cheese and the hot sauteed kale.
Arrange the potatoes on a baking sheet and return to the oven until hot, about 15 minutes. They also can be microwaved for 2 minutes. Serve hot, garnished with pumpkin seeds and chicken, if desired.