Preheat the oven to 400F/220C.

Using a sharp knife, slice through the raw sweet potatoes carefully, creating slits but not going all the way to the bottom so as not to break apart the potatoes. They're a little hard, so be cautious. Oil a roasting pan.

Rub or brush the sweet potatoes with a little olive oil and sprinkle with a little sea salt. Bake for about 20 minutes, or until they're tender enough so that you can fan them out like an accordion without them turning to mush or breaking.

While the sweet potatoes are roasting, make the pesto: Toast the pine nuts in a dry skillet until lightly golden. Place the pine nuts, chopped garlic, sage, mint, and cumin in the bowl of a food processor and pulse to combine. Drizzle in enough olive oil to create a wet, loose paste. Add the balsamic vinegar and season to taste with salt and pepper.

Remove the sweet potatoes from the oven, cool down a little so that they're comfortable enough to handle, and fan them out to widen the slits. Brush them generously with the pesto and pour over any excess. Place back in the oven and bake for ten more minutes. Remove and serve!

Note: If you're not Vegan or don't want to make this a vegan recipe, you can add 2/3 cup crumbled Greek feta to the pesto while processing.