• Preheat the oven to 180℃
• Heat oil in a non-stick pan, add onions, and cook for 15 minutes or till very soft
• Grease a 20cm round springform tin will oil
• Arrange pastries on a flat surface, alternating with oiling them
• Layer the pastries over one another at different angles
• Carefully place the pastry structure into the tin and fold any hanging ends into the tin
• Place the tin on a baking tray
• In a separate heat-proof bowl, place the spinach and add boiling water
• Drain the hot water and rinse with cold water, repeat
• Pat the spinach dry with a paper towel
• Arrange the onions, spinach, and grated cheese evenly on the pastry
• Whisk the eggs and milk in a medium-sized bowl, season with salt, pepper, and garlic
• Pour the eggs and milk mixture over the filling
• Place the tin in the oven
• Bake for 40 to 45 minutes or if a knife inserted into the center comes out clean
• Remove the tin from the oven and let it cool for 5 minutes
• Remove the quiche from the tin and cut it into wedges
• You can serve the quiche warm or cold

Notes:

• If you want a gluten-free quiche, use Gluten-free Shortcrust Pastry sheets or go crust-less!
• For a crust-less version, opt out of the pastry. Directly place the vegetable and cheese filling in the greased tin, pour the egg and milk mixture over it. Bake for 30 minutes or until a knife inserted comes out clean. You have yourself a crust-less spinach quiche.