Step 1

In a small skillet, toast the peppercorns over moderate heat until fragrant, about 30 seconds; let cool. Transfer the peppercorns to a mortar or spice grinder and grind to a powder. Put the shrimp in a bowl, toss with 1 teaspoon of the ground peppercorns and season with salt.

Step 2

In a medium skillet, heat 1 tablespoon of the vegetable oil. Add the shrimp and stir-fry over moderate heat until almost cooked through, 4 minutes. Transfer to a plate.

Step 3

Heat the remaining 3 tablespoons of vegetable oil in the skillet. Add the chopped scallions, garlic, jalapeños and chile and cook over moderate heat, stirring, until the scallions and garlic are softened, 5 minutes. Add the remaining 1/2 teaspoon of ground peppercorns and cook, stirring, for 1 minute. Add the shrimp and lime juice and stir until the shrimp are just cooked through, 1 minute. Season with salt and transfer to a bowl. Garnish with the sliced scallion, drizzle with the chile oil and serve.