Preheat oven to 375 degrees. Spray a medium casserole dish with non-stick cooking spray. Pour 1 cup of the sauce into baking dish and tilt dish to spread. Drizzle in 3 Tbsp heavy cream and stir . Add half the tomatoes. Bring a large pot of unsalted water to a boil. Cook gnocchi about 1/3 shy of the time listed on package . Drain gnocchi well then immediately transfer to baking dish and spread out. Sprinkle in remaining tomatoes, then pour remaining 1 cups sauce evenly over top*. Top with mozzarella cheese. Bake in preheated oven until sauce is bubbling, about 10 - 12 minutes. If you'd prefer cheese browned a bit then broil closer to broiler element during the last 2 - 4 minutes of that cook time. Garnish with basil and serve warm.