Prepare the Cilantro Lime Crema by adding the sour cream, cilantro leaves, lime juice, milk and sugar to the bowl of a food processor. Pulse until the cilantro is very finely chopped and the mixture is smooth and creamy.
Season to taste with salt and pepper, blend again and transfer to a small serving bowl. Set aside.
Put the avocado chunks, slaw, scallions and cilantro leaves in small serving bowls as well. Set aside until ready to serve.
Preheat the broiler for 10 minutes and line the bottom of a broiler pan with foil. Coat thoroughly with nonstick spray.
Note: if you don’t want to heat your house you can opt to grill the fish on a grill pan on the barbeque.
Wrap the tortillas tightly in foil and place them in the oven while the broiler preheats. Remove and set aside after about 7 minutes.
Season fish on both sides with salt and pepper, then drizzle the olive oil and lime juice on top and rub it into the fish with the back of a spoon.
Transfer the fish to the prepared pan and broil (or grill) just long enough for it to turn opaque. Fish cut into chunks shouldn’t take more than 3 to 5 minutes, whole fillets will take longer depending on how thick they are.
For whole fillets, figure two minutes per side for each 1/2-inch of thickness and once cooked, break into chunks for serving.
Transfer cooked fish to a serving bowl or plate and let your guests assemble their tacos at the table.
Place a portion of fish in the center of each tortilla, top with coleslaw and chunks of avocado and scatter a few scallions and cilantro leaves on top. Drizzle with the Cilantro Lime Crema.