Begin by preheating the oven to 375 F/190 C. Cook the bacon either in the skillet or you can also do it in the oven or even the microwave. Chop the onions and grate the cheese.
In a large bowl whisk together the eggs and the heavy whipping cream, half and half, or whole milk. Add the salt and pepper and whisk those in. The quiche batter is ready to go.
Add a cold pie crust to the tart pan and use your clean fingers to form it to the pan. You can make a homemade pie crust too if you like. You may also use a pie pan or even a square pan instead.
Next, add the chopped bacon and cheese to the tart pan or any other fillings you want to use, leave some of the cheese to go on top. Pour the quiche batter on top of the filling, then sprinkle the top with the remaining cheese. Note: if you plan to use lots of fillings you may need a large pan.
Bake the quiche in the oven, middle rack position, for 25 to 35 minutes, until a toothpick comes out clean when poked in the middle.
Allow the quiche to cool for about 10 minutes after it comes out of the oven. Then remove it from the pan, garnish with green onion if you like, and serve! Enjoy.