Step 1Cook the carrot in boiling water until it's tender, about 5 minutes. Drain and set aside.
Step 2Rinse the shrimp and scallops under cold running water and drain. Cut the scallops crosswise into 2 rounds.
Step 3Spray a wok with nonstick cooking spray and heat it over high heat until hot. Add the 2 ginger slices. When they begin to brown, push them to one side of the wok and add the seafood. Reduce the heat and stir-fry until the shrimp and scallops begin to brown, about 3 minutes. Remove them from the wok to a dish and cover to keep warm. Discard the ginger slices.
Step 4Wipe out the wok, then spray it again with cooking spray. Heat it over high heat until it's sizzling. Quickly cook the garlic, slivered ginger and green onions until tender, about 1 minute. Add the carrot and stir-fry until hot.
Step 5Blend the chicken broth and cornstarch until smooth, then stir the mixture into the vegetables along with the salt. Bring to a boil. Stir and simmer just until the sauce has thickened and is clear, then stir in the seafood and mushrooms. Heat just until hot all the way through, about 1 minute. To serve, spoon the seafood and vegetables over shredded lettuce.