Rangers came from behind to overturn a one-goal deficit as Steve Gallen’s side cancelled out Inter’s opener with a scintillating second half showing.
Three goals in 30 minutes from midfielder Mitchell – the first from the penalty spot – capped a remarkable comeback as the R's finished top of Group A, setting up a mouth-watering all English affair with Liverpool on Saturday in the process.
Ahead of the group decider, Gallen made two changes from the side which fired five past PDA last time out as Mark Smith returned between the sticks at the expense of Conor Hudnott while George Butler replaced Callum O’Sullivan in midfield.
Rangers were quickest out of the blocks, twice coming close to making the perfect start within three minutes.
Reece Grego-Cox found space in behind the Inter defence before picking out Olamide Shodipo, whose powerful stooping header was palmed over the bar by Ionut Radu in the Milan goal. From Brandon Comley’s resulting corner Cole Kpekawa rose highest but couldn’t prevent his header flying over the crossbar.
The early pressure sparked Inter into life, with a succession of near misses on the R’s goal. Federico Di Marco’s free-kick forced a fine one-handed save out of Smith before Darnell Furlong was forced to scramble Samuel Appiah’s downward header off the line.
Pedro Delgado was next to try his luck but his long-range effort drifted harmlessly wide before Appiah latched onto a long ball only to see his goalbound effort deflect wide.
Respite for Rangers came in the form of Grego-Cox’s foray forward shortly before the half hour mark. The R’s striker burst clear of his marker but could only shoot straight at the goalkeeper.
After seemingly weathering the storm, it was Inter who struck first with a stunning goal three minutes before the break. Enrico Baldini drifted inside before delivering a sumptuous effort into the top corner, leaving Smith motionless in the R’s goal.
Rangers went in search of an equaliser from the re-start, forcing the Italians deep at the start of the second half.
Grego-Cox - working tirelessly in attack - was finally rewarded for his efforts shortly before the hour mark, outpacing the Inter backline before being ceremoniously hauled down in the area. On spot-kick duties was Mitchell, whose penalty ballooned high into the top right corner to bring the R’s level.
Inter pressed for an immediate reply but the R’s defence stood firm while Delgado wasted a free-kick, blazing over from a dangerous position. The Inter frontman spurned an even clearer chance on 74 minutes as Di Marco’s pace posed problems down the R’s left. His cross fell perfectly for Delgado at the near post but the ball somehow squirmed wide.
It proved pivotal as the R’s were clinical at the other end when Mitchell doubled his tally following another surge from Furlong down the right. His inch-perfect cross found the midfielder, whose header soared into the top corner to edge Rangers in front for the first time.
With their tails up, Gallen's youngsters set the seal on a momentous victory two minutes from time as Mitchell completed a famous evening in style. After bursting onto Comley's knock down, he let fly with an unstoppable half volley into the far corner.
There was little time for Milan to react as Rangers closed out proceedings in the dying stages, safe in the knowledge their place in Saturday's final was soundly secured.
QPR: Smith, Furlong, Kakay, Comley (O’Sullivan 90), Wise, Kpekawa, Komodikis (Page 85), Mitchell, Grego-Cox (Mitford 79), Butler, Shodipo (Young 70).