Put fish in a deep fry pan with 5 cups water. Boil, reduce heat and simmer 8 minutes, until fish flakes easily. Drain and reserve liquid. Flake fish and throw away bones. ( I pull apart with fingers it just falls into flakes.) leave to cool.
Put potato, celery and onion in a lge saucepan with 3 cups of reserved liquid. (I like to add a carrot and sweet potato to my chowder, but this is optional) (Reserve rest of liquid if any left.) Bring to the boil than simmer 8 minutes or till tender. set aside. Cool.(I blend or mash the veg in the liquid. It's just a personal preference.)
Melt butter in a saucepan over low heat, add the bacon and cook 3 min. Stir in the flour, mustard and hot sauce, cook for 1 minute until pale and foaming.
Remove from heat and stir in the milk slowly, to start, while continuely stirring. Return pan to heat stirring until boils turn heat down and continue to stirr until it thickens (important to keep stirring so it doesn't stick and burn.) Stir into veggies and add any of the liquid if any remains
Add Parsley and fish, simmer over low heat for 5 minutes or until heated through. Season to taste, Serve with chopped parsley and cream (opt)
(I make it a hardier meal by adding corn kernels and peas to the simmer stage.)