the.com/upper crust

means The upper crust refers to the highest, most elite social class — the wealthy and well-born at the top of society.

from The popular story is that in medieval times, bread was baked with uneven heat, so the top of the loaf came out best — and by custom the finest, browned top crust was sliced off and given to the most important person at the table, while servants and lesser folk got the burnt bottom. The phrase is first recorded in English in the early 1800s meaning the social elite, and it almost certainly builds on 'crust' already meaning the outer, uppermost layer of something. The bread anecdote is charming and widely repeated, but there's no solid historical record proving it as the literal origin — it's best treated as a vivid folk explanation that happens to fit the metaphor perfectly rather than a documented fact.