Preheat your oven to 375°F (190°C). Prepare individual ramekins or scallop shells for serving. Pat the scallops dry with paper towels to remove excess moisture, which ensures a good sear during cooking.

In a large skillet, heat 2 tablespoons of olive oil over medium-high heat. Once hot, add the scallops in a single layer, making sure not to overcrowd the pan. Sear for 1-2 minutes on each side until golden brown. Remove the scallops and set them aside. Avoid overcooking to keep them tender.

In the same skillet, reduce the heat to medium and add the minced shallot. Cook for 2-3 minutes until softened and fragrant. Be careful not to let the shallot brown, as this can introduce bitterness.

Add the dry white wine to the skillet, using a wooden spoon to scrape up any browned bits from the bottom of the pan. Let the wine simmer for about 2 minutes until it reduces slightly, enhancing the flavour of the sauce.

Next, stir in the flour and cook for 1-2 minutes to form a roux, which will thicken the sauce. Gradually add the fish stock, stirring continuously to ensure a smooth mixture. Let the sauce simmer gently for another 3-4 minutes until it thickens to a light, velvety consistency.

Reduce the heat to low and stir in the heavy cream and butter, whisking until well incorporated. Season the sauce with salt, black pepper, and a squeeze of fresh lemon juice for a bright finish. Taste and adjust seasoning as necessary.

Place 3 seared scallops into each ramekin or scallop shell. Pour the cream sauce over the scallops evenly, ensuring they are generously coated. Sprinkle the top with grated Gruyère cheese and, if desired, a light layer of breadcrumbs for a crispy finish.

Place the ramekins or shells on a baking sheet and transfer them to the preheated oven. Bake for 10-12 minutes, or until the cheese is melted and golden on top. Garnish with fresh parsley before serving. Serve immediately with crusty French bread or a light green salad for a classic French meal.