Heat the oil in a deep, heavy skillet to 370 degrees on a deep-fry thermometer. Heat oven to 200 degrees. Set out a plate lined with paper towels. Put a wire rack over a baking sheet.

Finely chop the garlic, sprinkle 1/2 teaspoon of salt, then mash back and forth with the side of your knife across your cutting board until crushed to a puree.

Scrape into a medium bowl and add the oregano, black pepper, mustard, base, and beer. Add the flour and baking powder to the wet ingredients and whisk just until combined.

Mix crema, mayo, milk, lime juice and salt.

Cut the fish into pieces about 3 inches long by 1/2 inch square.

Use a pair of tongs to pick up a piece of fish, dip it completely into the batter, and lay it into the hot oil. Continue with a few more pieces of fish, filling the hot oil but not crowding it.

Fry, turning the pieces regularly, until deep golden and crisp, about 4 minutes. Drain on paper towels; then transfer to the rack. Keep warm in the oven while you fry the rest of the fish.

Serve fried fish pieces in tortillas with cream sauce, cabbage, salsa of your choice, and a wedge of lime.