This recipe is very good. I think it is from our dear friend RisaG from New Jersey, a collaborator at the Whats for Dinner Board.

Grilled Chicken Breasts Au Poivre (GF Grill)

6 large boneless skinless chicken breast halves -- skin on
2 chicken legs
extra-virgin olive oil
1/2 cup white wine
2 qt chicken stock
2 sprigs parsley
2 thyme branches
2 cloves garlic
salt
Optional:
red wine vinegar

For sauce: Remove the fillets from the chicken breasts. With a cleaver, chop each leg into 4 pc (I didn't do this). In a large, deep saucepan, brown the chicken leg pieces and the fillets in a little olive oil. When they are well browned, deglaze with the white wine and cover with the chicken stock. Bring to a boil, reduce to a simmer, and add the parsley, thyme, garlic and 1 tsp of peppercorns. Simmer 1 hour, then strain, reserving the cooked meat for another purpose, like ravioli stuffing. Skim off the fat. Reduce the broth until rich and slightly thickened; only about 1-1/2 cups should remain. The sauce can be prepared several hours ahead, or the day before. Preheat the GF Grill. While preheating, carefully pound the chicken breasts to flatten them slightly. Crack the rest of the peppercorns in a mortar & pestle or crush them on a cutting board with the bottom of a heavy pan (cast iron is perfect). Coat the breasts lightly with olive oil and season with salt and cracked peppercorns. When the GF is ready, spray with some olive oil spray and place chicken breasts on grill. Spray tops of chicken and close. Cook for 4 minutes. Remove to platter. Warm the sauce, check for seasoning, and add a few drops of red wine vinegar, if you wish. Serve the breasts whole or slice each one diagonally into 4 thick slices. Spoon on the sauce and serve.