Step 1

Preheat oven to 450°. Pierce potato several times with a fork or sharp knife. Roast potato on a rimmed baking sheet until tender, 35–45 minutes. Let cool, then scoop out flesh; discard skin.

Step 2

Meanwhile, combine kombu and 4 cups water in a large pot. Let sit until kombu softens, 25–30 minutes. Bring to a simmer over medium heat. Immediately remove from heat once water starts simmering; fish out kombu and discard. Add bonito flakes and stir once to submerge them. Return to a gentle boil, reduce heat, and simmer about 5 minutes. Remove from heat and let steep 15 minutes (this ensures you get the most flavorful broth, or dashi, possible). Strain dashi through a fine-mesh strainer into a medium bowl. Discard solids; wipe out pot.

Step 3

Transfer dashi to a blender. Add sweet potato, coconut milk, miso, and turmeric. Blend until smooth. Return to pot and bring to a very gentle simmer. Remove from heat and stir in lime juice.

Step 4

Divide soup among bowls. Top with coconut flakes and peanuts, then drizzle with chili oil.