In a large pot, heat the oil over medium high heat. Add the onions and stir, and once they start to sizzle, reduce the heat to medium. Stir and cook, reducing the heat to medium-low if they start to stick. Cook for as long as you have time, at least 10 minutes, up to an hour or two.
Add the sweet potato, kale, rosemary and stock and raise the heat to medium-high. Bring to a boil, cover and cook for about 10 minutes. When the sweet potato pieces are tender, take off the heat.
Transfer the soup to the Vitamix or food processor. If using the processor, puree without adding the almond milk. If using the blender, add the milk and puree. Add the salt and several grinds of pepper, and taste. Add more if needed.
Serve in bowls with toasted sliced almonds, and a rosemary sprig.