Preheat your oven to 375°F (190°C). Place your pie crust in a 9-inch pie dish and prick the bottom with a fork. Bake for 10 minutes until slightly golden. Remove from oven and set aside.

Sauté the Vegetables

In a skillet over medium heat, add a little oil or butter and sauté the diced onion until translucent. If using additional vegetables, add them to the skillet and cook until softened. Remove from heat.

Mix the Egg Mixture

In a mixing bowl, whisk together the eggs, heavy cream, salt, and pepper until well combined. Stir in the grated cheese, sautéed vegetables, and fresh herbs if using. If making the meat option, add the cooked bacon or sausage at this stage.

Assemble and Bake

Pour the egg mixture into the pre-baked pie crust. Bake in the preheated oven for 30-35 minutes, or until the center is set and the top is lightly golden.

Cool and Serve

Allow the quiche to cool for about 10 minutes before slicing. Serve warm or at room temperature.