The deal is the latest in Chelsea’s end of season players clear out as they seek to rebuild the team under new manager Mauricio Pochetinno.
Two goals from Kai Havertz and Mason Mount in the first half, gave The Blues a 2-0 victory, their first Premier League win since October.
Chelsea will now face Liverpool in the FA Cup final on May 14.
Mason Mount finally found a way past Everton goalkeeper Jordan Pickford in the 70th minute, only for teenage defender Jarrad Branthwaite to equalise four minutes later.
Bowen’s 56th minute goal for West Ham made the Hammers the first EPL side to score two goals against Chelsea this season.
The win was without Romelu Lukaku and Timo Werner, who both suffered injuries in Wednesday’s Champions League win over Malmo.
A first half goal by Chelsea’s record signing, Kai Havertz, was enough to deny the Citizens their first champions League trophy.
