Peel the onions and cut into thin slices. If you have food processor, can cut the onions in the food processor
In a heavy bottom pan, add in oil and the onions.
Turn the heat onto medium and heat the oil slowly
Cook the onions in the oil until they are wilted and turned colour.
Once the onions have turned colour, turn the heat to medium high and cook the onions until all the moisture have been cooked out and the onions are brown in colour.
Strain out the oil and leave it to cool
Put onions and oil into a clean jar OR put the oil in a clean jar and onions in another air tight container. This can be stored for up to 6 months.