Place all the cooked fillets to the oven. Wipe the pan clean and place over a medium flame. Add the 12 tablespoons of butter to the pan and let it melt, foam, subside, begin to bubble again, and turn a nutty brown. Immediately remove from the heat and carefully add the lemon juice, parsley, the remaining 1/2 teaspoon of salt, and several grindings of white pepper to taste. (Be careful as the butter will most likely spatter angrily when you add the lemon juice.)