Heat olive oil and 1 tablespoon of butter in a large skillet over medium heat. Add shrimp and scallops, sauté for 3-4 minutes until just cooked through. Season with salt and pepper, then remove from skillet and set aside.

In the same skillet, add the remaining tablespoon of butter and sliced mushrooms. Cook for 5-7 minutes until golden brown and tender. Add minced garlic and cook for an additional minute.

In a mixing bowl, combine the sautéed seafood and mushrooms. Pour in heavy cream and half of the grated Gruyère cheese. Mix well and season with additional salt and pepper to taste.

Preheat the oven to 375°F (190°C). Grease a baking dish and pour the seafood mixture into it. Sprinkle the remaining Gruyère cheese and breadcrumbs on top.

Bake in the preheated oven for 20-25 minutes until the top is golden brown and bubbly. Let cool slightly before serving.

Serve hot, garnished with fresh parsley and lemon wedges.