Ingredients
1/4 cup extra-virgin olive oil
3 tablespoons capers, drained and patted dry
1/2 cup chopped roasted hazelnuts
1 celery heart (pale center stalks and leaves), chopped (about 1 cup)
1 1/2 teaspoons whole-grain or stone-ground mustard
2 tablespoons sherry vinegar
Kosher salt and freshly ground pepper
1 head frisée, coarsely chopped (about 4 cups)
1 small bunch lacinato kale, stems and center ribs removed, shredded (about 4 cups)
Preparation
Heat 2 tablespoons oil in a small skillet over medium-high. When oil shimmers, add capers. Cook, stirring a few times, until they swell and darken slightly, 1 1/2 to 2 minutes. Add hazelnuts and cook 1 minute more. Transfer mixture (with oil) to a small bowl. Let cool completely, then stir in celery.
Meanwhile, in a large bowl, whisk together mustard and vinegar. Gradually whisk in remaining 2 tablespoons oil to make the dressing; season with salt and pepper. Add frisée and kale, tossing to evenly coat; let stand at least 20 minutes and up to 1 hour. Top with caper mixture before serving.
