OK if you are serious, the most important ingredient is the fish. I have more than 40 years experience of eating Fish and Chips in the UK and now my restaurants in the USA serve fish and chips to thousands of customers every year. To get an authentic texture and taste you should use North Atlantic Cod, its what the best restaurants in the UK use.
In the USA, California its almost impossible to get a fresh supply. Many restaurants in California use Pollock it's a nasty alternative wet greasy fish that they smother in thick chewy batter. I use the best cod I can buy, but it's only available in small pieces, the texture and flavor are very good. I also use a real beer batter that I have my staff mix fresh each day. We use real brown ale beer as it imparts a great flavor to the batter.
Next the fries, In the UK the fries are supplied frozen and pre cut, they take about 7 minutes to fry at 340 F. In the USA, I wanted something a little different so I use the Belgian method to fry my "Chips" thats what the Brits call fries. First you must use unfrozen potatoes to make your fries, if you use spuds ( potatoes ) that have been chilled or frozen your fries will go very dark before they are cooked. This is because all the starch has turned to sugar when kept too cold.
Anyway fry you chips at 340 F until you just see them turn very light brown, this will take about 2-3 minutes. Take them out of the frier turn them out on a sheet pan and dry off as much oil as possible with a clean towel. Leave for 2-3 hours Then when you are ready to serve toss them back in the frier with the temperature set to 370 F until they are a golden brown ( about 4 minutes) I should have said we don't peel our spuds we wash the skin 3 times in running water and cut them in a machine to about 3/8" square.
Experiment with oils, we use Canola clear not creamy but in your part of the world you will need to test to see that the oil does not add a nasty taste to the fries .
OK last thing in the UK we used to use old newspapers to wrap our fries, now they use unprinted news paper to overcome the ink problem. In the USA I have had news papers especially printed with vegetable oil inks so they look authentic and are safe to eat from.
P.S.
Second most important thing is the location of your restaurant, you can have the best Fish and Chip in the world but without a great location you can fail.
Good luck
