- 4 spring onions or 8 scallions, white parts only, spring onions halved lengthwise, quartered if large
- 4 tomatillos, husks removed, rinsed, quartered
- 1 large or 2 small nopales (cactus paddles), spikes removed
- 4 garlic cloves, finely chopped
- 4 ounces queso fresco
- 2/3 cup olive oil, divided
- Kosher salt, freshly ground pepper
- 3 tablespoons Sherry vinegar or red wine vinegar
- 1 teaspoon honey
- 1 teaspoon instant espresso
- Vegetable oil (for grill)
- 3 cups torn frisee
- 1 cup trimmed watercress
- 1/2 English hothouse cucumber, halved lengthwise, seeds removed, thinly sliced
- 1 cup fresh cilantro and parsley leaves with tender stems
- Combine onions, tomatillos, nopales, garlic, cheese, and 1/3 cup olive oil in a large resealable plastic bag; season with salt and pepper. Seal bag, pressing out air, and toss to coat. Let sit at least 1 hour.
- Whisk vinegar, honey, and espresso in a medium bowl until honey and espresso are dissolved. Gradually add remaining 1/3 cup olive oil, whisking constantly. Season with salt and pepper; set aside.
- Prepare grill for medium-high heat; lightly oil grates. (Or, heat a grill pan over medium-high.) Remove onions, tomatillos, and nopales from marinade; grill, turning occasionally, until tender and charred in spots, about 5 minutes. Let cool.
- Remove cheese from marinade and grill, turning often, until browned on all sides, 8-10 minutes; let cool.
- Cut vegetables into bite-size pieces; coarsely chop cheese.
- Arrange greens on a platter. Season with salt and pepper and drizzle with half of vinaigrette. Top with cucumber, herbs, and grilled vegetables and cheese; drizzle with remaining vinaigrette.
- Do Ahead: Vinaigrette can be made 2 days ahead. Cover and chill.