Try it once then make your own modifications.
I personally add dry dill or any other herb you may like, about 3 Tbsp
and a pinch of pepper
Ingredients
1 1/4 cup Flour
1 Tbsp Baking Powder
1/4 cup Cornstarch
1 Tsp Salt
1 1/2 cup Water
1 Tsp Vinegar
Method
Combine all ingredients and stir until
mixed then let sit in the fridge for about 30 minutes. If after a few
pieces, the batter is running off the fish, just add a bit of flour
and remix. You want it to stick and not fall off.