Prepare the tartar sauce by mixing all ingredients in a non-reactive bowl. Cover and refrigerate for a minimum of 2 hours.

Sift flour and baking powder together. Add salt and pepper. While whisking slowly add the beer. Mix in egg and refrigerate until use. If batter becomes thickened from sitting, add more beer to thin. Batter should be thinner than pancake batter but thick enough to coat a spoon when dipped into the batter.
Prepare a pot of hot oil or a portable fryer set at 350 degrees. Flour two or three fillets and take one at a time and dip into the batter. Remove from the batter and let the excess drain off the fillet. Now place the fillet carefully into the hot oil. In a short time, the fillet should rise to the surface and float. This is your opportunity to drop another piece in. By doing it this way, you're preventing multiple pieces from sticking together. Repeat until your fryer has 10 or 12 pieces dependent upon your space. Turn and submerge the pieces, so they cook evenly and are golden brown. This will take five minutes or so depending on the recovery rate of your fryer. When the pieces are done, remove them from the oil with a slotted spoon and
place them on a heated tray with paper toweling to drain slightly. Repeat the process until all the fish is fried.

Serve the fish with your favorite condiments: malt vinegar, tartar sauce or fresh lemon.