。
Mother tasted the soup and added a little more salt.
Literal
Mother [topic-は] soup [gen-の] taste [obj-を] looked-at and a-little-more salt [obj-を] put-in.
味を見る ('look at the taste') is a fixed idiom for tasting food — a cook's inspection, not just a casual sip. Note how 見る, normally about vision, extends here to the sense of taste; Japanese regularly uses 見る for checking or assessing (様子を見る 'see how things are', 脈を見る 'check the pulse'). The ~て form chains the tasting to the salting as sequential actions.