In a 3-1/2- or 4-quart slow cooker combine sweet potatoes, garbanzo beans, carrots, leek, garlic, chile peppers, and ginger. Stir in broth. Cover and cook on low-heat setting for 6 to 8 hours or on high-heat setting for 3 to 4 hours. Cool mixture slightly.
Transfer mixture, half at a time, to a blender or food processor. Cover and blend or process until smooth. Return all of the blended mixture to the slow cooker. Serve with Kale Chips and sour cream.
Preheat oven to 300 degrees F. Line a large baking sheet with parchment paper. Place kale leaves on the prepared baking sheet. Brush with olive oil. Sprinkle with salt. Bake for 20 to 25 minutes or until crisp.