Kale and Fennel Dense Bean Salad

Whisk the vinegar and mustard together in a large bowl. Slowly pour in the olive oil while whisking constantly. Whisk in 1/2 teaspoon salt and a few grinds of black pepper. Add the cannellini beans, kidney beans, chickpeas, tuna, fennel, celery, carrot and kale to the bowl. Toss until everything is evenly coated. Sprinkle with parsley, mint and chopped fennel fronds and gently toss. Taste and adjust the seasoning with more salt and pepper if desired. Serve immediately, or cover and refrigerate for up to 3 days. It gets even better as it marinates!