To make the crema, combine the sour cream, two chipotle peppers, 1 tablespoon of the adobo sauce they came in and a generous squeeze of lime juice in the jug of a blender (or use a food processor), then blend until smooth.
Season to taste and set aside.
Thaw the frozen shrimp then pat dry.
Add to a bowl then drizzle with olive oil and season generously with salt, pepper and a few tablespoons of taco seasoning and toss to coat in the spices.
Heat a grill pan over medium-high heat (or grill the shrimp on an outdoor grill/barbecue/braai) then cook the shrimp in batches for 1-2 minutes per side until they are golden and starting to caramelize.
To assemble the tacos, heat the tortillas in a large pan then add a generous spoonful of the crema.
Add shredded cabbage, chopped red onion and add the shrimp.
Add cubed avocado and garnish with fresh cilantro/coriander.
Serve immediately with extra lime wedges for squeezing.