Green’s Dictionary of Slang

brownstone front n.

[their brownstone houses]

1. [mid-19C–1900s] (US) meton., an aristocrat, a member of the upper classes who lives in such a building.

2. [late 19C-1900s] (US short order, also brownstone mansion) in catering use, as a play on sense 1.

(a) corned beef hash.

(b) steak.

(c) pork and beans; ham and eggs.

In phrases

put on a brownstone front (v.)

[mid-19C] (US) .