Creating the delicious Gourmet Seafood Cassolette is straightforward if you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 375°F (190°C).
2. Sauté Seafood: In a large skillet, heat the olive oil over medium heat. Add onions and garlic, and sauté until translucent.
3. Add Seafood: Add the shrimp, scallops, and fish. Cook for about 3-4 minutes until the seafood is just cooked through. Remove from heat.
4. Prepare the Sauce: In a bowl, whisk together the heavy cream, seafood stock, Old Bay seasoning, paprika, lemon juice, salt, and pepper.
5. Combine: Pour the cream mixture over the cooked seafood, gently folding to combine.
6. Transfer to Cassolette Dishes: Spoon the seafood mixture evenly into individual cassolette or oven-safe dishes.
7. Add Topping: In a separate bowl, mix the breadcrumbs and cheese together. Sprinkle this mixture on top of each cassolette.
8. Bake: Place the cassolette dishes on a baking sheet and bake for 25-30 minutes, or until the tops are golden and bubbly.
9. Garnish: Remove from the oven and allow to cool slightly. Garnish with fresh parsley before serving.

Following these steps will lead you to create an exquisite dish that captures the luxurious essence of seafood.