* skinless, boneless, about 1/2 lb each, halved ** the rind, pith, and membrane cut away with a serrated knife and discarded and the fruit chopped, reserving any juice In a ceramic or glass bowl, combine the oil, garlic, coriander, thyme, scallions, and the chicken breasts. Let them marinate, chilled, for at least 8 hours or overnight. In a saucepan, cook the shallots and the ginger in the butter over a monderately low heat, stirring, until the shallots are softened. Add the chopped lemons, limes, and oranges with all the reserved juices and simmer the mixture for 10 to 12 minutes, or until the liquid is reduced to a syruplike consistency. Add the broth, increase the heat to moderate, and boil the mixture, stirring occasionally, for 10 to 15 minutes, or until it is reduced by 1/3. Mix the cornstarch and water together. Stir in the cornstarch mixture, simmer the sauce for 30 seconds, and strain through a fine sieve into a bowl. Add the Grand Marnier, the white pepper, and salt to taste. Remove the chicken from the marinade and let it stand at room temperature for 15 minutes. Grill the chicken on a rack set about 5 inches above the mesquite, turning it once, for 10 to 12 minutes, or until it is just cooked through. Transfer the chicken to a platter, spoon the sauce over it, and garnish the platter with lemon wedges.
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