prepare the gremolata and shrimp
In a small bowl, combine the parsley, lemon zest and garlic. Season the shrimp with salt and pepper. In a large skillet, heat 2 tablespoons of the olive oil. Add half of the shrimp and cook over moderately high heat, turning once, until golden brown and just cooked through, 2 to 3 minutes per side. Add 2 tablespoons of the spiced butter to the skillet and cook until lightly browned; add 1 tablespoon of the lemon juice and toss to coat the shrimp in the sauce. Using tongs, transfer the shrimp to a serving platter. Strain the butter sauce through a sieve into a small bowl. Repeat with the remaining olive oil, shrimp, lemon juice and 2 more tablespoons of the butter. Season the butter sauce with salt and drizzle it over the shrimp. Top with the gremolata and serve.