Step 1

Heat a large heavy pot over medium and pour in oil. Add onion and carrots, season with a five-finger pinch of salt, and cook, stirring often, until vegetables are very tender and just taking on a hint of color at the edges, about 5 minutes. Lightly crush fennel seeds with a mortar and pestle, or roughly chop them. Add fennel seeds, curry, and mustard seeds to pot and cook, stirring, until fragrant (the mustard seeds may begin to pop), less than a minute. Add split peas, stir to coat, then add stock and 4 cups water. Increase heat and bring to a boil, then simmer, stirring occasionally and adding more water if soup looks too thick, until split peas are very tender and some are starting to disintegrate, 50–55 minutes.

Step 2

Mash soup with a potato masher until split peas are in small pieces and soup is textured but creamy (if you prefer a smoother soup, use an immersion blender directly in the pot). Taste and adjust seasoning with more salt.

Step 3

While the soup is simmering, lightly crush coriander, fennel, and mustard seeds.

Step 4

Heat oil in a small skillet over medium and cook coconut flakes and spices, stirring constantly, until spices are sizzling and coconut is golden brown, about 1 minute. Transfer to a plate, season with salt, and let cool (coconut will crisp as it cools).

Step 5

Serve soup topped with spiced coconut and cilantro.