Gwen Stefani has celebrated a special anniversary with fans, as "milestone" album The Sweet Escape turns 15.MORE: Gwen Stefani and Blake Shelton's holidays will be extra special this year - all the details "Happy 15th birthday to my second solo album!! #TheSweetEscape was such a milestone in my career, I hope it’s still satisfying your sweet tooth all these years later," she captioned the post which featured promo pictures for the release.WATCH: Gwen Stefani shares glimpse inside stunning new