1. Using scissors, cut down the back shell of each shrimp and remove the dark intestinal vein, leaving the shell intact. In a small bowl, combine the ketchup, sherry, chili sauce, lemon juice, soy sauce and sugar.
2. In a large skillet, heat 2 tablespoons of the vegetable oil. Add the deveined shrimp to the skillet and cook over high heat, turning once, until they start to curl and turn pale pink, about 2 minutes.
3. Add the remaining 1 tablespoon of oil to the skillet with the jalapeños, garlic, lemongrass and ginger and cook, stirring, until fragrant, about 1 minute. Add the scallions and the ketchup mixture and stir-fry for 30 seconds. Stir in the cilantro. Spoon the shrimp onto plates and serve with rice.