Preheat the oven to 375°F.
In a large skillet, heat the olive oil over medium heat. Add the chopped onion and sauté until translucent, about 5 minutes. Stir in the minced garlic and cook for an additional minute.
Add the mixed seafood to the skillet and cook for 3-4 minutes, just until the seafood is opaque. Remove from heat and set aside.
In a mixing bowl, combine the heavy cream, mozzarella cheese, Parmesan cheese, thyme, paprika, salt, and pepper. Stir in the cooked seafood mixture until well combined.
Transfer the seafood mixture to a greased baking dish. Sprinkle the breadcrumbs evenly over the top.
Bake in the preheated oven for 25-30 minutes or until the top is golden brown and bubbly.
Remove from the oven and let it cool for a few minutes. Garnish with fresh parsley before serving.