Simon Cowell The Ex Whisperer

2/26/2014 10:04 AM PST

Simon Cowell -- The Ex Whisperer

Simon Cowell
is the new Winston Churchill -- last night he took his current girlfriend AND his ex-fiancee out to dinner ... at the same time ... and somehow, it didn't end in World War 3.

Simon treated baby mama-GF Lauren Silverman and ex-fiancee Mezhgan Hussainy to a fancy dinner at Miami's Prime Fish, where they ate outside and basked in Florida's stifling humidity.

The three later emerged from the restaurant without a single scratch.

Guess Mezhgan wasn't lying when she said she was happy for Simon and his new girl -- the $8 million mansion Simon gave her probably didn't hurt either.