upper crust

Short definition from Wiktionary

Noun

1. 1
   The social elite, the highest social class.
2. 2
   Used other than figuratively or idiomatically: see upper, crust. The topmost layer of a bread, pastry dish, or other item with a hardened coating.

Adjective

1. 1
   Alternative form of upper-crust.
2. 2
   Posh, upper-class; pertaining to the upper crust.