Cook the Lentils:

Rinse the lentils under cold water. In a saucepan, combine lentils, bay leaf, onion halves, and enough water to cover the lentils by a couple of inches. Bring to a boil, then reduce heat and simmer for 25-30 minutes, or until the lentils are tender but still hold their shape. Drain and discard the bay leaf and onion.

Prepare the Vegetables:

While the lentils are cooking, sauté the garlic, carrot, celery, and red bell pepper in a skillet with a bit of olive oil until they are just softened. Set aside to cool.

Make the Vinaigrette:

In a small bowl, whisk together the olive oil, red wine vinegar, Dijon mustard, salt, and pepper.

Assemble the Salad:

In a large bowl, combine the cooked lentils, sautéed vegetables, parsley, and chives. Pour the vinaigrette over the salad and toss gently to combine.

Serve:

Adjust the seasoning if necessary. The salad can be served warm or at room temperature. Garnish with additional herbs if desired.