Lightly salt and liberally rub with lime juice about 1/2 kilo of fish fillets. Let them sit for about an hour if you have time, or as long as possible.
Meanwhile, slice at least 10 cloves of garlic and toast them in 3 tablespoons each of oil and butter. Don't let them burn or even get dark brown, but they'll be perfect when they're golden brown. Do it slowly over medium heat. Remove the garlic from the pan and set aside.
When the fish is done marinating, fry it in the remaining oil on both sides till just cooked through. Just before it's done, add the garlic back to the pan and some parsley if you like. Taste for salt and add 1 more tablespoon of lime.
This is based on a recipe from Authentic Mexican. Even if it doesn't taste Mexican.