Grilled Shrimp Tacos with Avocado-Corn Salsa

1. 1
   Remove the corn kernels from the cobs: Place a large container on a damp towel. Fold a paper towel into fourths and place it inside the container. Stand 1 ear of corn on the paper towel, using the stem as a handle. Using a paring knife, slice downward, letting the kernels fall into the container. Rotate the cob and continue until all the kernels have been removed; discard the cob. Repeat with the remaining corn. Discard the paper towel.
2. 2
   Add the scallions, tomatoes, measured lime juice, cilantro, serrano, and measured salt and stir to combine.
3. 3
   Halve and pit the avocados. Using a paring knife, score the flesh of the avocado halves in a 1/4-inch-wide crosshatch pattern (be careful not to cut through the skin). Using a spoon, scoop the avocado pieces into the corn mixture and gently fold to combine.
4. 4
   Taste and add more lime juice or salt as needed; set aside.

For the tacos:

1. 1
   Heat an outdoor grill to high (about 450°F to 550°F). Meanwhile, assemble the shrimp.
2. 2
   Whisk the lime juice, oil, chipotle powder, salt, and cumin together in a large bowl. Add the shrimp and toss to combine.
3. 3
   Skewer each shrimp through the tail and head ends, leaving about 1/4 inch of space between each shrimp. Transfer the skewers to a baking sheet.
4. 4
   Place the skewers in a single layer on the grill without touching. Close the grill and cook until grill marks appear on the bottom, about 4 minutes. Flip the skewers, close the grill, and cook until the shrimp are just firm, about 1 minute more. Transfer the skewers to a clean baking sheet.
5. 5
   Remove and discard the skewers, transfer the shrimp to a cutting board, and coarsely chop. Place in a serving bowl.
6. 6
   Serve the shrimp with the tortillas and salsa.