Add the remaining 1 tablespoon oil, scallions and garlic. Cook, stirring, until fragrant, about 15 seconds. Add peas; cook, stirring often, until bright green, 2 to 3 minutes. Add the reserved sauce mixture; cook, stirring, until thick, about 1 minute. Return the chicken to the pan; cook, stirring, until heated through, about 1 minute more.