- 3/4 pound onions, finely chopped
- 2 teaspoons olive oil
- 2/3 cup French green lentils, picked over and rinsed
- 1 cup fat-free chicken broth
- 1 cup water
- 1/2 teaspoon salt
- 1/8 teaspoon black pepper
- 1 1/2 tablespoons coarsely chopped fresh dill
- 4 tablespoons coarsely chopped fresh flat-leaf parsley
- 6 (6 ounce) skinless boneless chicken breast halves
- 1 teaspoon arrowroot
- 2 tablespoons fat-free chicken broth
- 1 1/4 cups fat-free chicken broth
- 2 1/2 teaspoons fresh lemon juice, divided
- 1 tablespoon coarsely chopped fresh mint
- 1/2 pound Bibb lettuce, leaves separated (torn if large)
- 1/4 cup crumbled feta
- Cook onions in oil in a 12-inch heavy nonstick skillet over moderately low heat, stirring frequently, until deep golden brown, 25 to 30 minutes. Transfer to a medium bowl, reserving 3 1/2 tablespoons onions in a small bowl for stuffing and sauce. (Do not clean skillet.)
- While onions are browning, simmer lentils in 1 cup broth and 1 cup water in a 3-quart saucepan, uncovered, stirring occasionally, until just tender, 20 to 25 minutes. Drain lentils in a sieve, then stir into onions in medium bowl along with salt and pepper. Cool to room temperature.
- Stuff chicken breasts: Stir together dill, 3 tablespoons parsley, 2 tablespoons reserved onions, and salt and pepper to taste in a small bowl. Pat chicken dry and cut a 3- to 4-inch-long pocket horizontally in thicker side of each chicken breast. Gently stuff chicken breasts with herbed onions, then season chicken with salt and pepper.
- Grill chicken: Prepare grill for cooking. If using a charcoal grill, open vents on bottom of grill, then light charcoal. Charcoal fire is medium-hot when you can hold your hand 5 inches above rack for 3 to 4 seconds. If using a gas grill, preheat burners on high, covered, 10 minutes, then turn off burner directly below where chicken will go and reduce remaining burner(s) to moderately high.
- Grill chicken, covered only if using a gas grill, on lightly oiled grill rack, turning over once, until cooked through, 8 to 11 minutes total. Transfer to a plate and let stand, loosely covered, while making sauce.
- Make sauce and assemble salad: Stir together arrowroot and 2 tablespoons broth in a small bowl. Puree remaining 1 1/2 tablespoons reserved onions with remaining 1 1/4 cups broth in a blender until smooth, then pour into skillet and deglaze by boiling over moderate heat, stirring and scraping up brown bits, 1 minute. Reduce heat to low, then add arrowroot mixture and cook, stirring, until just thickened, about 1 minute (do not let boil). Stir in 1/2 teaspoon lemon juice and season with salt and pepper. Remove from heat and keep warm, covered.
- Stir mint, remaining tablespoon parsley, and remaining 2 teaspoons lemon juice into lentils, then toss with lettuce and season with salt and pepper. Slice chicken, then divide salad among 6 plates and top with chicken, feta, and sauce.