For the Lime Crema

1. In a small bowl, stir together the sour cream, fresh lime juice and salt.

For the Shrimp Tacos with Corn and Bacon

1. In a large nonstick skillet over medium-high heat, fry the bacon, stirring frequently, until crispy and golden, 7 to 8 minutes. Using a slotted spoon, transfer the bacon to a paper towel-lined plate, leaving the bacon fat in the skillet.
2. Add the corn to the fat in the skillet and season with ¼ teaspoon salt. Cook the corn, stirring frequently, until crisp, about 2 minutes. Spoon the corn into a bowl and set aside.
3. Add the shrimp, scallions, garlic, cumin, chili powder, and ⅛ teaspoon salt to the skillet. Cook, stirring frequently, until the shrimp are opaque and cooked through, 3 to 4 minutes.
4. Add the corn, bacon, cilantro, and 1 tablespoon lime juice to the shrimp. Stir to combine, then taste and adjust the seasoning with more lime juice or salt, if necessary. Remove from the heat and cover to keep warm while you heat the tortillas.
5. Warm the tortillas in the microwave or in a skillet according to the package instructions. Place the tortillas on serving plates and top with the shrimp mixture and generous spoonfuls of the lime crema. Serve the rest of the crema on the side.
6. Make-Ahead Instructions: The lime crema can be made up to four days ahead of time and stored in a covered container in the refrigerator. The shrimp mixture can be made one day ahead of time and refrigerated; just keep the cooked bacon and cilantro separate until you reheat the dish. Reheat the shrimp mixture in a skillet over medium heat until just heated through.