Step 1

Coarsely grind coriander seeds, fennel seeds, and peppercorns in spice mill or with mortar and pestle. Cook oil, garlic, and ground spices in a large saucepan over medium heat, stirring often, until garlic is softened but not crisp, about 2 minutes. Add scallions, chile (if using), and lemon zest and cook, stirring occasionally, until scallions are softened and almost completely charred, 5–7 minutes.

Step 2

Pour 6 cups cold water into saucepan, increase heat to medium-high, and bring to a simmer. Add leeks, fennel bulb and stalks, beans, and sugar snap peas (pan will look crowded but vegetables will shrink as they cook). Reduce heat to medium. Add a large pinch of salt and simmer, stirring occasionally, until leeks, fennel, and sugar snap peas are fork-tender, about 5 minutes. Add spinach, English peas, and miso and cook, stirring, just until spinach is wilted, about 10 seconds; season with salt.

Step 3

Divide soup among bowls. Top with fennel fronds.

Step 4

Do Ahead: Soup can be made 1 day ahead. Transfer to an airtight container and chill.