In a large pot, heat olive oil over medium heat. Add chopped onion and minced garlic, stirring frequently until the onion becomes translucent, about 5 minutes.

Stir in the diced sweet potatoes and vegetable broth. Increase heat to high and bring to a rolling boil, then reduce to medium-low and let simmer for 10 minutes until sweet potatoes start to soften.

Cover the pot and let the soup simmer for 20-25 minutes, stirring occasionally, until the sweet potatoes are tender and easily mashable.

Using an immersion blender, blend the soup in the pot until smooth. If using a standard blender, transfer in batches with caution.

Stir in the chopped kale and let the soup simmer for an additional 5 minutes. Adjust seasoning with salt and pepper as needed.