Preheat the oven to 180°C (350°F). Lightly spray a 20 cm (8 inch) round springform cake tin with a removable base with oil, or grease with melted butter. To prevent any leakage, wrap foil tightly around the outside of the base and sides of the springform tin.
For the bacon mixture, fry the bacon over medium-high heat until the fat has rendered. If using low-fat bacon, heat 1 tablespoon of olive oil in the pan before adding the bacon. Add the garlic and onion, then sauté until the onion softens, about 2 minutes.
For the egg mixture, whisk together the eggs, cream, Dijon mustard, 1 tablespoon chives, salt, and pepper in a large bowl until well combined.
Evenly distribute 3/4 of the bacon mixture over the base of the cake tin, then sprinkle 3/4 cup of shredded cheese on top. Pour the egg mixture over the cheese, then top with the remaining cheese, chives, and bacon mixture.
Bake for 30 to 35 minutes, or until the centre of the quiche is just set. It should still look soft but should not jiggle too much. Be careful not to over-bake, as this will cause the quiche to lose its custard-like texture.
Leave the quiche in the tin for 5 to 10 minutes. Run a knife around the edges to loosen, then carefully release the springform and remove the sides.