Lentil Salad with Balsamic Vinaigrette

1 1-inch-thick slice red onion, plus 1 c. chopped red onion
3 fresh parsley sprigs, plus ½ c. chopped fresh parsley
2 garlic cloves, minced (divided)
1 c. lentils, rinsed and drained
2 tbsp. olive oil
3 tbsp. balsamic vinegar
2 tsp. Dijon mustard

Bring medium saucepan of water to boil. Add onion slice, 3 parsley sprigs and 1 minced garlic clove and bring to boil. Stir in lentils. Reduce heat and simmer uncovered until lentils are just tender, about 20 minutes. Drain. Discard onion and parsley. Stir oil, vinegar, mustard and remaining garlic in small saucepan over low heat until just warm. (Do not boil.) Place warm lentils in bowl. Add chopped onion, chopped parsley and warm vinaigrette; toss to coat. Season with salt and pepper. Serve warm or at room temperature. Serves 4.