- 1 serrano chile, seeds removed, chopped
- 1 cup (packed) cilantro leaves with tender stems
- 1/2 cup olive oil
- 1/2 teaspoon ground caraway
- 1/2 teaspoon ground cumin
- Kosher salt, freshly ground pepper
- 1 pound brussels sprouts
- 1 tablespoon olive oil
- 6 small citrus (such as navel or blood oranges or tangelos)
- 3 tablespoons Champagne vinegar
- 2 teaspoons poppy seeds
- Kosher salt
- 1 cup fromage blanc or plain whole-milk Greek yogurt
- 1 teaspoon nigella seeds (optional)
- Purée chile, cilantro, oil, caraway, and cumin in a blender until smooth; season with salt and pepper.
- Trim brussels sprouts; halve lengthwise. Pluck off outer green leaves and place in a large bowl. Very thinly slice half of brussels and add to bowl with leaves. Heat oil in a medium skillet over medium-high. Cook remaining brussels, tossing occasionally, until crisp-tender, about 5 minutes. Transfer to bowl.
- Trim ends from citrus; cut off peel and white pith. Cut 3 citrus in half lengthwise, then thinly slice crosswise. Working over a bowl, cut along membranes of remaining 3 citrus to release segments. Squeeze membranes and trim over bowl to release juices. Whisk 3 Tbsp. juice, vinegar, and poppy seeds in a small bowl; season dressing with salt. Discard remaining juice.
- Add citrus and dressing to bowl with brussels sprouts and toss; season with salt.
- To serve, spread fromage blanc over a platter. Arrange salad on top and drizzle with 1/4 cup green harissa (save remaining harissa to use on roasted veg or grilled meat); sprinkle with nigella seeds, if using.
- Harissa can be made 3 days ahead. Cover and chill.