Chai-Spiced Sweet Potato Soup

2 pounds Japanese yams or white sweet potatoes

3-4 Tbsp. ghee, divided (can also sub coconut oil to make it vegan) 

1 tsp. kosher salt

1 medium yellow onion, diced

4 cloves garlic, minced

1/2 tsp. kosher salt

1/2 tsp. group cinnamon

1/2 tsp. ground ginger

1/2 tsp. ground cardamom

1/2 tsp. ground coriander

1/8 tsp. ground nutmeg

1/8 tsp. white pepper

4 cups low-sodium vegetable broth

1 14-ounce can full-fat coconut milk

1. Preheat oven to 425 degrees F. Line a large sheet pan with parchment paper, and set aside.
2. Cut the sweet potatoes in half lengthwise. Brush each cut side with ghee and sprinkle with kosher salt. Place the sweet potatoes cut-side down on the prepared sheet pan. Roast sweet potato halves at 425 degrees F for 50-55 minutes, or until easily pierced through with a fork. Remove cooked sweet potatoes from the oven and let cool for 1 hour, or overnight in an airtight container in refrigerator.
3. After sweet potatoes have cooled and skins removed, begin preparing the soup. Heat a large Dutch oven over medium heat on the stove. Add remaining ghee and diced onion. Saute onion until translucent, about 7-8 minutes. 
4. Add the minced garlic and saute about 1 minute, stirring frequently. 
5. Add salt and spices (cinnamon, ginger, cardamom, coriander, nutmeg, and white pepper) and toast about 1 minute, stirring frequently, until fragrant. 
6. Add the vegetable broth to the pot and stir, scraping up anything stuck to the bottom. 
7. Using your hands, roughly break up the cooled sweet potatoes into pot. Stir to combine. Bring the mixture up to a boil, then reduce the heat to medium-low and let simmer 8-10 minutes, until sweet potatoes are heated through.
8. After sweet potatoes are heated through and soft, remove the pot from the heat. Use an immersion blender to puree the mixture until smooth. (Or transfer in batches to a blender to puree, and return the mixture to the pot.)
9. Return the pot to the stove on low heat and stir in the can of coconut milk until combined. Let the coconut milk heat through for a minute or so, and then serve immediately. 
10. Serve soup hot, garnished with an additional drizzle of coconut milk. Store leftovers in an airtight container in the refrigerator for 3-4 days.