Blend 1 cup of flour with 2 Tbsp cornstarch, 1/2 tsp salt, 1/2 tsp garlic powder, 1/2 tsp dill and 1/2 tsp pepper
Beat two egg whites until stiff enough to hold peaks
Mix 8 ounces of Lager/Pilsner beer with 8 ounces of room temp. water
Add the yolk of one egg to the liquids and whisk until foaming
Pour the liquids into dry ingredients and stir just long enough to thoroughly combine. Much like a pancake batter, you'll have a few lumps but don't let that trouble you
Fold in the beaten egg whites
Dip the fish into the batter and shake off excess batter, then roll in panko bread crumbs and deep fry (try 400 degrees and move down to 375 if that's too hot)
I prefer to use a cast iron dutch oven for my deep frying so I can't recommend a commercial stand-alone deep fryer. I've tried them; don't like them for their lack of good temperature control.
I use both Lodge and Griswold. If you try the formula you may find it necessary to adjust the amount of liquid, depending on the type of flour you select. I use Pillsbury AP flour. I should also have mentioned that the herbs and spices you use is a matter of personal choice. I've found that tarragon, thyme, oregano, red pepper flakes and other herbs and spices work well as a means of varying the flavor profile, depending of course on the type of fish selected.
Another variation, instead of the panko bread crumbs, use crushed dried onion flakes.