Japanese Sweet Potato Soup Recipe

Heat the sesame oil in a large pot over medium heat. After 90 seconds when the oil is hot, add the onion and sauté for 6-8 minutes, until translucent.
Add the garlic, ginger, white pepper, and shichimi togarashi, if using. Continue to sauté for 2 minutes, stirring frequently to sweat the aromatics.
Add the sweet potatoes and vegetable stock. Bring to a boil, then reduce the heat and simmer for 20-22 minutes, until the sweet potatoes are completely tender.
Remove the pot from the heat and stir in the coconut milk, miso, tamari, and rice vinegar.
Transfer the soup to a blender in batches and blend until completely smooth. If you have one, you can use an immersion blender right in the pot instead.
For the optional tempura sweet potatoes, heat the frying oil in a deep, heavy-bottomed pot over medium-high heat. After 5-6 minutes, check the oil temperature; it should be around 350°F (175°C). Meanwhile, whisk together the flour, cornstarch, baking powder, and salt. Add the ice-cold sparkling water and stir just until a loose batter forms.
Toss the julienned sweet potato in the batter, allowing excess batter to drip off. After the oil has reached 350°F (175°C), carefully add the battered sweet potato in small batches. Fry for 2-3 minutes, turning occasionally, until crisp and lightly golden. Transfer to a wire rack or paper towel-lined plate.
Ladle the soup into bowls and garnish with tempura sweet potato strips and the furikake and scallions.