。
A good cook doesn't throw out yesterday's soup.
Literal
Cooking [possessive-の] skillful person [topic-は] previous [possessive-の] day [possessive-の] soup [object-を] doesn't-discard.
うまい (skillful) is a colloquial synonym of 上手. The phrase 料理のうまい人 is a relative clause where うまい modifies 人 with 料理の specifying the domain of skill. Using 前の日 rather than 昨日 gives it a timeless, proverbial quality — this reads as general wisdom about cooking rather than a specific event.