Warm Lentils with Mustard Vinaigrette

Name: Warm Lentils with Mustard Vinaigrette
Ingredients: 1 1/2 cups black lentils; 2 bay leaves; 2 cloves garlic, smashed; 1 stalk celery; 1 small bundle fresh thyme; 1/2 carrot, peeled; 1/2 fennel bulb; 1/2 red onion, peeled, root end left on; Kosher salt; Olive oil, for sauteing; 1/2 carrot, finely diced; 1/2 fennel bulb, finely diced, plus fennel fronds, for garnish; 1/2 onion, finely diced; 1 clove garlic, smashed; 1/2 cup red wine vinegar; 3 tablespoons whole-grain mustard; 1 tablespoon chopped fresh parsley