One 4-inch piece of lemongrass, inner white bulb only, cut into strips
One 1-inch piece of fresh ginger, peeled and cut into matchsticks
1 tablespoon fresh lime juice
1 teaspoon finely grated lime zest
1/4 teaspoon crushed red pepper
Pinch of kosher salt
Pinch of sugar
24 medium shrimp (about 3/4 pound), shelled but with tails left intact,
In a small nonreactive saucepan, combine all of the ingredients except the shrimp and bring to a boil. Transfer to a bowl and let cool, then refrigerate until chilled or for up to 1 day.
Prepare an ice water bath. Cook the shrimp in a medium saucepan of boiling salted water, stirring occasionally, until pink, about 2 minutes. Drain the shrimp and plunge into the ice bath; drain again and pat dry. Transfer the shrimp to a platter and serve with the dipping sauce.