Cut the onions in julienne as finely as possible. Be sure to slice them the same thickness.
Then separate and spread them on a plate so that they are not stuck together.
Put a pan with plenty of oil on medium-high heat.
When the oil is hot, add the onions and stir. Fry them on medium heat.
When you see that the onions are started to change the colour lower the heat.
When they are golden brown, remove and put them on a wide plate.
Carefully spread them all over the plate and let them cool.
They will turn crispy when they are cool. Use them on the same day or you can store them in a ziplock bag into the freezer.