From Longman Dictionary of Contemporary Englishtop something ↔ off phrasal verbCOMPLETEto complete something successfully by doing one last thing Let’s top off the evening with a drink. → top→ See Verb table
Examples from the Corpus
top off• Needless to say, the top subsequently shoots off.• To top it all off, a girl wants to join the band!• And to top it all off, he was gorgeous.• Then the wind rose again and plucked his top hat off his head and sent it bowling among the stones.• To top this off, they cake on makeup like plaster on a sheet of drywall.• At the same time I think some people are going well over the top in slagging off Wilko.• But topping the sandwich off with enough shredded lettuce to make Cesar Chavez spin in his grave is not.• Then the carrier top will slip off your head and crash down and crush your wrists. 