Heat 2 tablespoons olive oil and 2 tablespoons butter in a large skillet over medium heat. When the butter melts and begins to foam, add the minced garlic and chopped shallot. Sauté, stirring, until fragrant and translucent, about 1–2 minutes. Add the red pepper flakes if using and stir for 15 seconds.

Cook Shrimp & Crawfish

Increase heat to medium-high. Add the seasoned shrimp to the skillet in a single layer and cook 1–1.5 minutes per side until pink and just cooked through. Remove shrimp to a plate and set aside.

Add the remaining 1 tablespoon olive oil to the skillet. Add the crawfish tails and sauté 1–2 minutes just to warm through and develop a little color. Season crawfish with a pinch of salt and pepper. Return the shrimp to the pan.

Deglaze & Make Sauce

Pour in 1/4 cup dry white wine (or chicken broth) to deglaze the pan, scraping up browned bits with a wooden spoon. Let the liquid reduce by about half, 1–2 minutes. Stir in lemon juice and the remaining 1/2 teaspoon salt if needed. Taste and adjust seasoning.

Finish with Cheeses & Herbs

Lower heat to medium-low. Sprinkle the shredded mozzarella evenly over the seafood in the skillet, followed by the grated Parmesan. Cover the skillet with a lid for 1–2 minutes until cheeses melt and form a creamy top. If you prefer a browned top, place the skillet under a preheated broiler for 1–2 minutes — watch carefully to avoid burning.

Remove from heat, sprinkle chopped parsley over the dish, and drizzle with a little extra-virgin olive oil if desired.

Serve

Serve immediately with crusty bread slices to soak up the sauce or over cooked pasta. Pass extra lemon wedges at the table.