Wrap the tortillas in aluminum foil and place in the oven until soft and pliant, about 12 minutes. Remove and keep wrapped until ready to use.
In a large pot or deep fryer, heat the oil to 350 degrees F over high heat.
In a large bowl, beat the egg with the milk and water. Add the flour, Essence, and baking powder, and whisk to make a thin batter. Dip the fish in the batter, turning to coat, and shake to remove any excess. Fry in batches in the oil until golden and crisp, about 1 1/2 to 2 minutes. Remove, drain on paper towels, and season lightly with the Essence. In a large bowl, mix the cabbage with the sour cream, lime juice and cumin, tossing to coat.
To serve, place 1 or 2 pieces of the fish inside each tortilla and top with some of the shredded cabbage. Squeeze with lime juice, and top with salsa to taste. Garnish with cilantro and serve immediately.
Roasted Tomatillo Salsa:
Preheat the oven to 400 degrees F.
Place the tomatillos, garlic and onion on a baking sheet. Drizzle the vegetables with the olive oil. Season with salt and pepper. Roast the vegetables in the oven until browned and softened, about 15 to 20 minutes. Remove the vegetables from the oven and place the tomatillos and onion in a food processor. Squeeze the garlic cloves out of their peels into the food processor. Add the jalapeno, juice of 1 lemon and lime to the vegetables. Pulse until the mixture is fully incorporated but not pureed. Season the salsa with salt and pepper, to taste, and set aside.