Shell the shrimp, leaving the tail and the shell of the last joint intact. Reserve the shells. To make the broth, place the shrimp shells and the broth ingredients in a saucepan. Bring to a boil, lower the heat, and simmer about 20 minutes. Strain. Reserve ¾ cup.
Sprinkle the shrimp with salt and pepper, then dust with flour. Heat 3 tablespoons of the oil in a large skillet. Fry the shrimp quickly, about 1½-2 minutes. Remove the shrimp to a warm platter. Leave any remaining oil in the pan.
Place the parsley in a blender or food processor with ¼ teaspoon salt and the garlic. Blend until the ingredients are finely minced. With the motor running, pour in the shrimp broth and the wine. Blend until smooth.
Add the remaining 2 tablespoons of oil to the skillet. Sauté the onion until it is wilted. Stir in the 1½ tablespoons of flour and cook a minute. Gradually stir in the sauce from the blender. Cook until the sauce is thickened and smooth. Replace the shrimp in the skillet and cook only until they are heated through. Add salt and pepper to taste. Serve with a reserve white wine, such as Federico Paternina, and Ensalada a la Almoraina.