Combine the 4 cups shredded green cabbage, 1 cup shredded purple cabbage, 2 medium carrots, 1 small red onion, 3 large scallions, and 1 jalapeño in a large bowl.
In a medium bowl, whisk the 1/2 cup mayonnaise, 1/2 cup plain Greek yogurt, 1/4 cup fresh lime juice, 2 tablespoons granulated sugar, 1 teaspoon ground cumin, and 1 teaspoon chipotle powder, if using, until smooth and creamy.
Pour the dressing over the cabbage mixture and toss to combine. Season with sea salt and freshly ground black pepper to taste. Cover and refrigerate for at least 20 minutes before serving and up to 2 days. (If refrigerating for more than an hour or so, drain off any liquid that pools at the bottom of the bowl just prior to serving.)
Make the fish tacos
In a shallow bowl, combine the 1/3 cup all-purpose flour, 1 teaspoon chipotle powder, and 1 teaspoon finely ground sea salt, or to taste. Pat the 4 mild white fish fillets dry and lightly dredge in the flour mixture, shaking off any excess flour.
Heat 1 tablespoon oil in a skillet over medium heat and place 2 fillets at a time in the pan. Gently fry for 3 to 6 minutes, until the underside of the fish turns opaque. Use a spatula to flip the fillets and cook until opaque throughout. Place on a paper towel-lined plate, drain the remaining oil from the pan, and repeat with 1 tablespoon oil and the remaining 2 fillets.
To serve, for each fish fillet, heat the 8 small corn tortillas in a clean skillet in batches with the 1 remaining tablespoon oil, flipping them once, then place them on a plate.
Assemble the tacos
Cut each fillet in half and divide the fish evenly among the tortillas. Toss the slaw to recombine and then add a spoonful to each taco along with some cilantro leaves, if desired.
☞ TESTER TIP: Chances are you will have leftover slaw. Just cover it, stash it in the fridge, and serve it alongside pulled pork, grilled chicken, or just about anything.
Notes
Gluten-Free Fish Tacos Variation
Simply skip the step where you dredge the fish in flour and instead sprinkle the fish with the chipotle powder and salt.