Shell and devein shrimp, leaving tails attached; rinse an drain well. Combine
butter and oil in skillet; heat over medium heat until butter is melted and foamy.
Add garlic, chiles, lime juice and salt; cook and stir 1 minute. Remove from heat.
Spread shrimp in even layer in shallow baking dish. Pour hot butter mixture over
shrimp. Bake shrimp, stirring once or twice, just until opaque throughout and sizzling
hot, 10 to 12 minutes, being careful not to overcook.
Garnish with scallion; serve immediately. Use hard rolls or bolillos to sop up