Best Fried Fish Tacos

Combine onion, carrot, and jalapeño in a large heat-safe bowl or jar. Combine vinegar, lime juice, sugar, cumin and coriander seeds if using, and 1 teaspoon kosher salt in a small sauce pan and heat until boiling. Pour mixture over onions and jalapeños and let sit for 30 minutes, or refrigerate until ready to use.  Combine cabbage and cilantro in a large bowl and refrigerate until ready to serve. Right before serving, add 3 tablespoons pickling solution from the onions and jalapeños. Toss well and season to taste with salt. Combine sour cream, mayo, and chipotle in a small bowl and stir to combine. Cut fish into 1” to 1 ½”  thick strips, pat dry with paper towels, and season with salt. Preheat oven to 200° and fit a baking sheet with a metal cooling rack.  In a large bowl, combine ½ cup flour, cornmeal, cornstarch, 1 teaspoon kosher salt, and baking powder. Whisk to combine, then add beer and whisk until smooth. Place remaining ½ cup flour in a shallow bowl. In a large, heavy-bottomed pot over medium heat, heat 1 ½” to 2” oil to 350°. Coat one piece of fish with flour, then dip in batter and let any excess batter drip off. Gently lower fish into oil, then repeat twice more.  Fry fish until golden, about 2 minutes per side, then transfer to prepared cooling rack and place in preheated oven. Continue to fry fish in batches and transfer to oven to keep warm. Add 1 to 2 pieces fish to the center of each tortilla. Top with chipotle sauce, slaw, and pickled onions and serve with lime wedges on the side.