Before starting, ensure your kitchen is clean and organized. Gather all your ingredients, measuring tools, and cooking utensils.

In a large skillet, place the butter over medium heat. Allow it to melt slowly, ensuring it doesn’t brown.

Once melted, add the chopped onion to the skillet. Sauté for about 3–4 minutes until the onion is translucent. Then, add minced garlic and sauté for an additional minute, stirring constantly to prevent burning.

Gently add the shrimp and scallops to the skillet. Cook for about 3 minutes, stirring occasionally until the shrimp turn pink and the scallops become opaque.

Pour in the white grape juice and let it simmer for 2 minutes.

Stir in the heavy cream, salt, and black pepper. Mix everything well, allowing the sauce to thicken slightly.

Carefully transfer the seafood mixture into a baking dish. Spread it evenly.

Generously sprinkle your choice of grated cheese over the top of the seafood mixture.

Preheat your oven to 180°C (350°F). Once hot, place the baking dish in the oven and bake for about 15 minutes, or until the cheese is bubbly and golden brown.

Remove the gratin from the oven and allow it to cool slightly. Serve immediately.