For the quiche:
1 (9-inch) uncooked pie crust in a disposable pan, thawed for 10 to 15 minutes if frozen
6 large eggs
3/4 cup heavy cream
1/2 teaspoon kosher salt
1/4 teaspoon freshly ground black pepper
1/2 cup coarsely chopped fresh basil leaves
4 ounces mini fresh mozzarella balls (sometimes labeled as pearls)
For the tomato topping:
1/2 pint cherry tomatoes, quartered
2 tablespoons balsamic vinegar
1/4 teaspoon kosher salt
Arrange a rack in the middle of the oven and heat to 425°F. Prick the pie crust all over with a fork. Bake until lightly browned, 10 to 15 minutes.
Meanwhile, whisk the eggs, cream, salt, and pepper in a large bowl until combined. Stir in basil; set aside.
Let the crust cool for 10 minutes. Meanwhile, stir the tomatoes, vinegar, and salt together for the tomato topping. Reduce the oven temperature to 375°F.
Once the crust is cool, place the mozzarella balls in an even layer on the crust. Pour the egg mixture over the mozzarella. Bake until the quiche is just set and the top is lightly browned, 45 minutes to 1 hour. Let cool 5 minutes before slicing and serving with the balsamic tomatoes.