Crispy fried shallots are an essential condiment in Vietnam. They turn up in soups (pho) and on salads, sprinkled onto dumplings as a garnish, and minced and added to meatballs. Crispy, sweet, and salty, they are indispensible. You may want to make double batches, as people have a hard time resisting the urge to snack on them. Strain the oil you used to fry the shallots and use it in other recipes or to fry more shallots. The strained oil, called shallot oil, will keep, refrigerated, for several weeks. The shallots should be used the same day they are fried.