Peel and slice shallots even and thin, about ⅛ inch (3mm), you will get about 1 to 1½ cup of sliced shallots.
Put shallot slices in a small pot, pour cold oil in the pot and cook it over medium heat.
Meanwhile, get the drainer, a plate lined with paper towel and a heat proof container for the drained oil ready.
Once it starts boiling, adjust the heat to medium low to low and continue to cook, stirring occasionally. Cook just until most of the shallots turn golden (see the picture in the post), then immediately remove the pot from the heat and drain the oil (save it for other usage).
Lay the shallots on a paper towel over a plate and sprinkle with a pinch of salt if using. Once it cools completely, it will become golden brown and crispy.
Put the crispy shallot in an airtight container and the shallot oil in a glass jar and store them in the fridge.