Step 1

Preheat oven to 350°. Toast cashews on a rimmed baking sheet, tossing once, until golden brown and fragrant, 7–10 minutes; let cool and coarsely chop.

Step 2

Meanwhile, finely chop fennel bulb and thinly slice stalks. Heat oil in a large pot over medium-high. Add mustard seeds and cook until seeds begin to pop, about 1 minute. Add fennel bulb and stalks, scallions, and sweet potatoes and cook, stirring occasionally, until fennel begins to soften, 3–4 minutes. Add cauliflower, chiles, and turmeric; toss to coat. Reduce heat to medium, add 3 Tbsp. water, and cook, covered, until cauliflower is just tender, 6–8 minutes. Uncover and stir in garam masala, ½ cup cashews, ¼ cup cilantro, and ¼ cup fennel fronds; cook until fragrant, about 2 minutes.

Step 3

Divide fennel mixture among bowls. Top with remaining ½ cup cashews, ¼ cup cilantro, and ¼ cup fennel fronds.