Remove the fish from the water, rinse and dry with paper towel, to remove as much of the water as possible. Cut into smaller pieces.

Prepare the batter by mixing the milk, water, salt and baking soda together in a bowl, then begin adding flour a tablespoon at a time, and whisking for about 4 or 5 minutes once it becomes the right consistency. The whisking is important. Check out the photo below to see the consistency of the batter.

Heat the oil in a pan over medium high heat. When it is hot, begin dipping the pieces of fish into the batter, which should be somewhat thick, and not too runny (you don't want all the batter running off the fish as you put it in the oil).

Place a few pieces of fish into the hot oil and fry until they are cooked through, about 4 to 5 minutes total (turning the fish half way through), or longer if it's a thicker piece of fish. If it browns to quickly, the oil is too hot.

Place on a paper-towel lined plate to soak some of the oil.

Continue with the rest of the pieces of fish. Place all the fish on a serving plate, garnish with some parsley and lemon slices, if desired and serve hot.