Preheat the oven to 400°F (200°C). Place the pie crust on a baking sheet, prick with a fork, and blind bake with parchment paper and dried beans for 10 minutes. Remove from oven and set aside. Reduce temperature to 350°F (175°C).
Cook bacon in a skillet over medium-high heat for 5-6 minutes until crispy, then remove and set aside. In the same skillet, cook onions for 4-5 minutes until softened, then remove and set aside.
Whisk together 5 eggs, 1 cup heavy cream, 1/2 tsp salt, and 1/2 tsp pepper in a medium bowl to make the custard.
Assemble the quiche: Layer half of the cooked bacon, onions, and 1/2 cup shredded cheese in the pie crust. Pour the egg custard over and top with the remaining bacon, onions, and cheese.
Bake at 350°F (175°C) for 40 minutes or until the top is set and the crust is golden brown.
Cool for 10 minutes, slice, and serve with optional fresh herb garnish.
Store leftovers in an airtight container in the fridge for up to 3 days or freeze for up to 1 month.