Saute onion in avocado oil in a large pot for 3-5 minutes.
Add garlic and cook for 2 minutes.
Add diced sweet potatoes, carrots, thyme, sage, sea salt and pepper.
Place on medium-high heat, cover and cook 15 minutes. Stir occasionally to prevent onions from browning.
Add 4 cups vegetable broth and bring to a boil, cooking for 15 minutes or until sweet potatoes are softened.
Using an immersion blender or food processor, puree the mixture uintil mostly smooth.
Place soup in a bowl and enjoy with fresh chives, avocado and croutons.