Preheat the oven to 230°C.
Halve the sweet potatoes lengthwise and cut each half into 3 long spears. Place them on a sheet pan and toss with the olive oil.
Spread the potatoes in one layer. Combine the spice mix, brown sugar, salt, and pepper and sprinkle on the potatoes.
Bake for 15 minutes and then turn with a spatula. Bake for another 5 to 10 minutes, until lightly browned. Sprinkle lightly with salt and serve hot.
For the La Boite Spice Mix:
Into a bowl add the turmeric, basil, chili, and mustard seed. Grind together in pestle and mortar or a clean coffee grinder the black pepper and coriander seed and add to the other spices.
Grind together the cumin and caraway seed as above and add to the spices and mix everything together.