Brighton needed just eight minutes to take the lead as Pascal Gross followed up after goalkeeper Zach Steffen had saved Solly March’s initial attempt.
However, Boro were back in it within five minutes when Jason Steele could only touch Chuba Akpom’s header from Ryan Giles’ cross on to the post and saw the ball ricochet in off him.
The Seagulls regained the lead with half an hour gone when Mitoma turned Solly March’s cross back across goal and Adam Lallana had the simplest of tasks to head home from point-blank range.
The top-flight side enjoyed the better of the possession as the whistle approached, but Boro continued to threaten on the counter as the half ended with Brighton leading 2-1.
Alexis Mac Allister got his chance as a half-time replacement for Lallana, and he made an impact within 13 minutes when he reacted smartly to flick full-back Pervis Estupinan’s shot past the helpless Zack Steffen and inside his left post to make it 3-1.
The Argentina star helped himself to a second with 10 minutes remaining when he turned Gross’ cross confidently past Steffen to make it 4-1.
It was soon five when another substitute, Deniz Undav, fired home with an excellent right footed finish after good work from March.
9. Adam Lallana 6-10
Played for 45 minutes and got forward well for his goal, which he chested into the back of the net. Will relish facing his former club Photo: NIGEL RODDIS
10. Mitoma 6-10
Teed-up Lallana for his goal. Not at his best today but did what he had to do. Should have been booked for a dive at the end of the first half Photo: NIGEL RODDIS
11. Evan Ferguson - 6-10
No goal for Ferguson this time out but led the line well and provided a focal for the Brighton attack. In contention to face Liverpool. Photo: Jan Kruger
12. Alexis Mac Allister - 9-10
What a display. On for Lallana at halftime. Clever flick to score the third goal and a lovely first time finish for the fourth. He also hit the post with a bending freekick. Full of confidence and more minutes in his legs ahead of the Liverpool match. Photo: Stu Forster