Preheat your grill or oven to medium-high heat.
Brush the split langoustes with a little vegetable oil or olive oil and season with salt and black pepper.
If using a grill: Place the langoustes cut-side down on the grill. Cook for about 5-7 minutes, then flip and cook for an additional 5-7 minutes until the meat is opaque and cooked through.
If using an oven: Place the langoustes cut-side up on a baking sheet. Bake in the preheated oven for about 10-15 minutes until the meat is opaque and cooked through.
While the langoustes are cooking, heat the vegetable oil or olive oil in a large skillet over medium heat.
Add the minced garlic and chopped onion. Sauté until the onion is translucent and fragrant.
Pour in the white wine and cook for 2-3 minutes, allowing it to reduce slightly.
Stir in the coconut milk and vanilla bean seeds. Cook for an additional 5-7 minutes, or until the sauce has thickened slightly.
Add the fresh lime juice and season with salt and black pepper to taste.
Arrange the cooked langoustes on a serving platter.
Spoon the vanilla sauce over the langoustes.
Garnish with chopped fresh parsley or cilantro.
Enjoy your meal!