Combine salsa ingredients in a bowl; mix and set aside.

In a large bowl, combine flour, cornstarch, baking powder, and salt.

In a separate bowl, blend beer with egg.

Pour into flour mixture and whisk until there are no more lumps.

Place fish onto a lined baking sheet. Pat dry.

Sprinkle flour over both sides of fish, then dip into batter.

Heat one inch of oil in a medium-sized pot.

When oil is hot enough, fry fish until golden, approximately one to two minutes.

Remove from pot and drain on a paper towel–lined baking sheet.

Combine sauce ingredients in a one-pound container.

Using an immersion blender, blend until smooth.

To assemble tacos, place two to three cubes battered fish in each taco.

Place tomato salsa over fish.

Top with a drizzle of hot white sauce.