Okay, you are opening a pandora's box with this one. Bring on the variations boys!!!
I'm sure that heavy cream or at least half and half would be preferable but I'm fat and had some 2% in the fridge so I started out with a 1/2 gallon of that. Based on this I put a half stick of butter in to compensate for the lack of butter in the milk(and therefore increase the amount of fat making goodness that was missing from the get go). Frankly, I coulda used more. Then I chopped a really big onion, about thumbnail sized, and about 5 small/medium sized baker potatoes skin on, scrub them good or you'll get dirt in it. This took about 5 minutes. You can put some celery or corn in too if you like but I passed on those because I was in a hurry. I get that started and then season as I go. This time I put some taragon in, maybe about a half tblspn...that's a powerful spice but I always like how it complements the potatoes in particular. I poured some sea salt in my palm and slowly worked my way up the salt chain as the process went on. Don't over salt obviously as it cooks down it'll get saltier. I also dumped some powdered chicken stock in...maybe a tblspn, which is also salty so be careful but this is a flavor maker. Black pepper and a nice big heaping tblspn of minced garlic. I left it at a high simmer for about 20 minutes and dumped the fish in...whatever you have and be generous. I even dumped in a small half bag of "salad shrimp" I had in the freezer that I bought last week for steelhead bait. Let it simmer a while and then I sifted some flour in and lightly whisked it so as to not beat the potatoes and onions into mush. The flour, milk and butter will thicken after a while but I wasn't looking for Chunky style thickness, just a little heavier so I didn't use much flour at all, maybe a third cup if I had to guess. Then I chopped some fresh parsley up I had on hand...maybe about a quarter to third cup and threw that in. I stared at the spices for a while and almost started gettin' silly but this is a basic recipe that was never intended to be elaborate. Simmer it and be careful with the fire because you can wreck it real quick with a burnt bottom. If you can lift the grate off an adjacent burner then stack them and tone the fire down a bit on the bottom of the pot. I don't do lectric burners so I can't help you with that.
The kids jumped on it right out of school but it was too early to eat it. I just had a little cup and it gets much better with time like most soups and stews, and women. Enjoy!