Peel the onions and and cut them into halves. Slice them as thin as possible to yield crispier barista. Make sure that you should cut them evenly.
Heat oil in a pan and when the oil is medium hot, add onions in it. If you making onion barista in large quantity, then add as much onions as the pan can easily adjust. Don't overcrowd the pan.
Let the onions fry and you keep on stirring them.
After couple of minutes the onions will become translucent.
After some more time, they will turn slightly pink in color. Keep stirring.
After some more time, the edges of onions will begin to turn brown. Keep stirring.
At last, the onions will turn brown. Don't make them extreme brown because even after removing the onions from the oil, their cooking process will keep on continuing being extremely hot.
Take the onions out from the oil and spread on some paper nepkin so that the excess oil is soaked.
Let them turn cool completely. Onion barista will become crunchy.