Heat the olive oil in a large skillet over medium-low heat. Cook the garlic slices until tender, but not brown. (This will take one minute or less.) Transfer with a slotted spoon to paper towels and reserve.

Turn the heat under the pan to high. Quickly toss the shrimp with the salt and pepper in a bowl. When oil is nearly smoking, add the shrimp. Saute, stirring and shaking the pan to prevent sticking, 3 to 4 minutes or just until the shrimp are still slightly undercooked. Remove from the heat. With a slotted spoon, transfer the shrimp to a platter, leaving as much liquid as possible in the pan.

Return the pan to the burner and reduce the heat to medium. Add the garlic slices and anchos and cook, stirring frequently, until the oil begins to turn orange from the chiles. Stir in the fish stock or clam juice, along with the shrimp and any juice that has collected on the platter. Add the lime juice and parsley, bring to a boil and remove from the heat. Serve immediately over white rice.