P.F. Chang's China Bistro
From The Big Bang Theory Wiki
An American Chinese Restaurant chain [1]. There is a P.F. Chang's at 260 East Colorado Boulevard, Pasadena -- very close to Leonard's and Sheldon's apartment.
On Valentine's Day in 2010 they have a "Lover's Special" for $39.95, and Howard takes Bernadette to spend the evening there (0315).