How to Make It
Preheat oven to 350°F. Roast hazelnuts in a single layer on a rimmed baking sheet until golden brown and fragrant, 8 to 12 minutes. Let cool. Rub hazelnuts between your fingers to loosen skins; discard skins (some will stick—that’s OK). Transfer hazelnuts to a cutting board and roughly chop; set aside.
Whisk vinegar, honey, salt, mustard, and pepper in a medium bowl. Slowly whisk in oil.
Toss kale and Brussels sprouts with ¼ cup dressing in a large bowl. Using your hands, massage dressing into kale mixture until leaves are slightly softened and shiny, about 2 minutes. Let stand for 10 minutes. Add pomegranate seeds and remaining dressing and toss to combine. Serve immediately or refrigerate overnight.
Just before serving, add croutons and hazelnuts and toss to combine.