Cut the onion lengthwise in half and thinly slice following the grain. Cut bacon into small dice.
Heat butter in a frying pan and sauté bacon. Add onions, salt, and pepper and cook over medium heat for 10 minutes. When onions are slightly colored, add maple syrup and sauté, turning off the heat when onions become caramelized. Let cool.
Mix eggs, milk, and fresh cream in a bowl and add salt and pepper, to taste.
15 ml (1 tbsp.) Canadian maple syrup (amber)
Roll out the pastry sheet until it is about 2-3 mm thick, spread in the pie plate, cut off excess pie dough, and prick vent holes all over the bottom of the sheet with a fork.
Place 3 into the pie plate in 5, and pour the sauce from 4 over the mixture. Top with Parmigiano Reggiano and bake in a 200°C (400°F). oven for 20 minutes first, then bake at 160°C (300°F) for 5 minutes. The quiche is done when the top is browned. Cut into easy-to-eat slices and plate.