Heat oil in dutch oven over med-high heat. Add leeks and saute 5-7 minutes. stir in tomato paste, peanut butter, harissa, garlic, turmeric, and cumin cook 1 to 2 minutes stirring constantly. Add broth, sweet potatoes, and 1 1/2 c water. Simmer over med-low heat, partially covered for 25 minutes or until sweet potatoes are tender.
Remove from heat and blend mixture with immersion blender (add more water if too thick). Bring soup back to a simmer and stir in spinach.