Fabio Carvalho made it 3-0 after the break before Mitrovic’s first of the game gave Fulham a 4-0 lead.
Bobby De Cordova-Reid made it 5-0 and things out worse for Luton when Ivory Coast star, Jean Michel Seri made it 6-0 with 10 minutes to play.
Mitrovic wrapped up the win and title with his second and Fulham’s seventh of the evening in stoppage.
Fulham will play in the Premier League next season after winning promotion at the first time of asking after they were relegated last season.