Shallots

Related to onions and garlic botanically (all are alliums), but shallots have a milder, more nuanced flavor.

Preparing: Peel, slice, and chop them like onions.

Best cooking methods: sautéing, roasting; deep-frying for garnish when sliced thin

When are they done? When tender and translucent

Other vegetables you can use: scallions are closest; onions (especially red or white), leeks