Prepare langoustines by cutting along the underside of the tail with kitchen scissors and removing the meat, or leave in shells. Pat dry with paper towels.

Heat olive oil in a large skillet over medium-high heat. Add langoustine tails and cook for 2 minutes without moving.

Flip langoustines and cook for another 1-2 minutes until opaque. Remove from pan and set aside on a warm plate.

Reduce heat to medium, add butter to the pan. Once melted, add minced garlic and cook for 30 seconds, stirring constantly until fragrant.

Pour in white wine and simmer for 1-2 minutes to reduce slightly, scraping up any flavorful bits from the pan bottom.

Return langoustines to pan with lemon juice, parsley, and red pepper flakes if using. Toss gently to coat. Season with salt and pepper to taste.

Transfer to serving platter immediately, drizzle with pan sauce, garnish with lemon wedges and extra parsley. Serve hot with crusty bread.