Preheat oven to 410oF (210oC). Line a baking sheet with parchment paper.
Chop sweet potato into 1/2 inch slices. Fill a pot with water and bring to a boil. Place sweet potato in a steaming basket and steam for 7 to 10 minutes. Transfer into a bowl and mash with a fork. Season with salt and pepper to taste.
Meanwhile, heat 1/3 of the olive oil in a pan over medium heat. Saute onions until soft, then add garlic and kale. Heat until kale is wilted.
In a small bowl, whisk together the balsamic vinegar, remaining olive oil, salt and pepper to taste. Drizzle about 1/2 the balsamic vinaigrette over the kale and stir until well coated.
Lay a brown rice tortilla on the baking sheet. Spread mashed sweet potato and top evenly with kale mixture. Cover with another tortilla and bake for 10 to 15 minutes or until golden brown and crispy.
Slice and serve with remaining balsamic vinaigrette.