Preheat oven to 200°C/Gas 6
Cover the tart base with baking parchment and fill with baking beans, bake blind for about 15 minutes.
Meanwhile, slice the bacon into strips and finely chop the onions.
Fry the bacon in a heavy based pan until it begins to get crispy, remove from the pan.
Add the onion and cook until soft finally add the chopped garlic and cook for 2 minutes.
Whisk the milk, cream and eggs together.
Remove the pastry from the oven and reduce the heat to 180°C/Gas 4.
Sprinkle the onion, bacon and parsley over the base of the tart then pour in the liquid.
Place the tin on a baking tray and return to the oven, bake for about 30 minutes until just set in the middle and golden brown.