In a small bowl, whisk together the chicken broth, mirin, and cornstarch. Set aside.

Heat the oil in a large nonstick frying pan or large wok over high heat. Add the scallions, garlic, and crushed red pepper flakes, and cook, stirring, until fragrant, 30-45 seconds. Add the scallops to the pan and cook, stirring occasionally, for 2 minutes, until mostly opaque. Fold in the sugar snap peas, then add the broth mixture. Cook, stirring, for 2-3 minutes, until the sauce is thick and glossy and the scallops are opaque, but are still moist in the center (cut one to check). Fold in half of the basil and remove from heat. Transfer to a serving dish, and top with the remaining basil.