Preparation Using a small knife or kitchen shears, butterfly shrimp from tail to base of head, leaving peel and head on; devein. Heat 3 tablespoons oil in a small saucepan over medium heat. Add garlic and pepper flakes; saut&eactue; until aromatic, about 30 seconds. Transfer to a medium bowl; stir in Pernod and 1 tablespoon fennel fronds. Season with salt and pepper. Add prawns; toss to coat. Marinate at room temperature, tossing occasionally,for 30 minutes. Prepare a grill to high heat. Grill prawns, brushing with marinade from bowl, until bright pink and just opaque in center, about 2 minutes per side. Transfer to a plate. Mix sliced fennel bulb and arugula in a large bowl. Drizzle lemon juice and remaining 2 tablespoons oil over; toss to coat. Season with salt and pepper. Arrange salad on a plate. Top with shrimp, garnish with 1 tablespoon chopped fronds.