For the cilantro lime sour cream: Combine the sour cream, garlic, jalapeño, lime juice, cilantro, 1/2 teaspoon salt and 1/2 teaspoon pepper in a small bowl and set aside.
For the red cabbage slaw: Combine the lime juice, cabbage, onion, oil, sugar and 1/2 teaspoon salt in a large bowl and massage for 2 minutes to soften the cabbage and distribute all ingredients evenly.
For the fish: Mix the cayenne, cumin and paprika with 1/2 teaspoon salt and a few turns of pepper in a dish and sprinkle all over the fish. Put the flour in a shallow dish and season with a pinch of salt and pepper. Beat the egg with 1 tablespoon water in another shallow dish, then put the breadcrumbs in a third shallow dish and season with salt and pepper.
Coat the fish all over in the flour and then the egg and then the breadcrumbs.
Heat a large skillet over medium-high heat and add a thin layer (about 1/4 cup) of oil. Fry the fish until golden and crispy, 4 to 6 minutes per side. Transfer to a cutting board and chop into strips.
To serve: Fill paper bags with chips (or open small bags of store-bought ones) and crush them coarsely. Top with a big plop of cilantro-lime sour cream, some fish, a squeeze of lime, slaw, avocado, jalapeños and a pile of fresh cilantro. Enjoy!