You can find the original recipe at the TROPICAL LIFE, FOOD AND FUN blog http://www.tropicallifefoodandfun.com/fresh-fish-with-key-lime-butter-sauce/

Ingredients:

800-900 g fresh fish filets (cod, hake, gilthead…)
salt

For the sauce:
1 cup water
¼ cup white wine (Chablis or Chardonnay)
1 tbsp freshly squeezed key lime juice
½ teaspoon garlic powder
freshly ground white pepper – to taste
120 g butter
3 teaspoons water
3 teaspoons starch

For frying:
2 eggs
2 tbsp water
1 cup flour
2 cups breadcrumbs

For the garnish:
1 cup diced tomatoes
1 cup scallions, finely sliced
½ cup coarsely grated parmesan
2 tbsp chopped parsley leaves

Method:

Place 1 cup water, wine and lime juice over high heat and reduce by half. This takes about 5 minutes. Add the garlic powder (and pepper to taste). Add 1 tbsp of butter at a time and whisk each time until the butter is incorporated. Repeat until all of the butter is used.
Mix 3 teaspoons water and the starch in a bowl and add to the sauce. Increase the heat to medium and stir until the sauce thickens and a few bubbles appear. Set aside.
Combine the chopped tomatoes, scallions and parsley leaves in a bowl.
Mix the eggs and 2 tablespoons of water in a small bowl. Coat the fish filets with the flour, dip into the egg wash and then coat with the bread crumbs.
Heat 4 tablespoons of the prepared sauce in a large skillet. Add the fish and sauté for 3 – 4 minutes on each side.
Place the fish on a serving plate. Spoon some sauce over the fish. Sprinkle with the combined tomatoes, scallions and parsley, and finally with the Parmesan cheese.
Optionally, you can add more sauce.