\phantomsection - how to jump to the chapter title instead of the center of the page (only)

The command \phantomsection sets the label at the current position. However the command chapter has previous and and skip below the title. Based on the last skip the position of \phantomsection is specified. To provide the label at the top of the page use the following order:

\cleardoublepage%\clearpage in onside mode
\phantomsection
\chapter*{Chapter Title}

If you use a KOMA class you can also use the command \addchap which simplefy the the lines above to

\addchap{Chapter Title}