Twice now I've tried pan frying fillets of white fish (Swai and Flouder) in olive oil and butter. Both times the fish has disintegrated into unsightly mush. Is there some technique I'm missing? How can I pan fry without the fish falling apart?
When we pan fry white fish, we use a non-stick but do not marinade nor bread it.
I definitely like what @moscafj said "flip once".
I am going to stick to your statement of "pan frying". - which is indeed different from deep frying, shallow frying, sauteing, stir frying. Looking at your description you seem to be mixing pan frying and stir frying...
So let's stick to pan frying which uses minimum quantity of oil.
Tip1: Try not to get a fillet as thick as 1 feet (I am exagerating). But really a standard 1cm-2cm kind of a fillet would be easier to handle & cook if you are novice.. (salmon can be particularly thicker)
Tip2: When fish is marinated with a base of oil and lemon - it helps alot by making the outer layer rougher, tastier since herbs are absorbed into fish and you may not even need extra oil to fry the fish.
Tip3: Don't over-crowd your pan by adding a population of fillets into the pan at once. Add two fillets with a relatively good space between them - based on the pan size and fillet size you use. So the heat distributes evenly among them.
Tip4: This is probably the cheapest non-stick pan I have ever used - lighter and durable even I want to throw it away. And it's like one of those old Beetle cars - no matter what you do - it just lasts... You can start with a pan like this and go up as you mature with the frying experience.
Tip5: The most important out of all, get your fish monga to give you fresh fish. If you are not aware how to choose a fresh fish, then you gotta do some research and get familiar with that. Personally I never ever use or recommend those frozen fillets (like "forgotten" dori fish) in hypermarket freezers. You get a good fish, you will enjoy a good meal.
Tip6: Don't forget to use a Fish Slice kitchen tool that's made for pan frying - if you aren't using one yet.
Reference link for you to get an understanding of frying techniques:
[Frying techniques vary in the amount of fat required, the cooking time, the type of cooking vessel required, and the manipulation of the food. Sautéing, stir frying, pan frying, shallow frying, and deep frying are all standard frying techniques.
Sautéing and stir-frying involve cooking foods in a thin layer of fat on a hot surface, such as a frying pan, griddle, wok, or sauteuse. Stir frying involves frying quickly at very high temperatures, requiring that the food be stirred continuously to prevent it from adhering to the cooking surface and burning.
Shallow frying is a type of pan frying using only enough fat to immerse approximately one-third to one-half of each piece of food; fat used in this technique is typically only used once. Deep-frying, on the other hand, involves totally immersing the food in hot oil, which is normally topped up and used several times before being disposed. Deep-frying is typically a much more involved process, and may require specialized oils for optimal results.](http://en.wikipedia.org/wiki/Frying)
When working with flounder or sole fish, they are so delicate that are almost guaranteed to break on you. However, if you do this simple steps, your chances of mushing or breaking comes down.
1) Do not bring the fish to room temperature and keep it cold until ready for sautéing.
2) Do not marinate or bread them, however dip them in white flour to coat and shake the excess. Make sure the oil in the pan is hot, then place the fish. This provides a little protection.
3) These fishes really need 2 minutes per side when sautéed. Leaving them any longer to get a darker color is not worth it and will break or mush the fish. However if you use butter as your oil option, the fish will have a better fried color even in that short cooking time.
4) Use a metal fish turner utensil to help you flip them as neatly as possible.