Torres helped Chelsea book another visit to Wembley after a relatively comfortable victory at Stamford Bridge.
Early goals from Gary Cahill and Salomon Kalou set the Blues on their way as Roberto Di Matteo maintained his 100% winning start to his tenure as Chelsea boss.
Torres added the third after 67 minutes to end a spell of 25 hours 41 minutes of football for Chelsea without scoring.
His second came five minutes from time as he flicked home a near-post header with Raul Meireles also scoring in the last minute.
Jermaine Beckford and Ben Marshall grabbed the consolation goals for Leicester, who will now go back to trying to force themselves into the Championship play-off picture.
Torres has shown glimpses of his former self in recent weeks and the Spaniard was instrumental again against the Foxes, with his goal coming after several decent efforts and good link-up play.
Chelsea started the better of the two sides with Torres looking lively from the outset.
It did not take long for Chelsea to take the lead as Cahill rose at the far post to head home Mata’s 12th-minute corner to open the scoring.
The ex-Bolton player celebrated by revealing a shirt in support of former team-mate Fabrice Muamba.
Torres was again involved as Chelsea doubled their advantage six minutes later as he broke into the Leicester half and outpaced Konchesky before sliding in Kalou, who finished calmly past Schmeichel.
Moments later, Torres should have broken his duck as he was found in the centre of goal by Mata, but headed straight at Schmeichel.
The visitors struggled to keep possession for any meaningful length of time as their supporters continued to cheer them on from the packed Shed End.
The Foxes responded and Beckford fired wide before Neil Danns had their first decent effort on goal in the 33rd minute as he forced Cech into a smart save at his near post.
Chelsea sat back and allowed Leicester to keep possession in and around their penalty area but restricting them to long-range efforts.
Cahill then took the ball away from Danns’ toe as he broke into the box as Chelsea eased to half-time.
Florent Malouda was introduced by Di Matteo at half-time and stung the palms of Schmeichel with a long-rang effort on 51 minutes.
Torres had another chance just before the hour mark but his left-footed effort was deflected clear as the Chelsea supporters willed their £50million man to find a goal.
The visitors then started to come forward with more purpose as David Nugent was stopped on the edge of the box before Lloyd Dyer flashed a shot just wide.
The moment the home supporters had longed for came in the 67th minute as Torres squeezed Meireles’ pass into the corner to score his first goal in over 25 hours.
The Spaniard almost grabbed another but his effort two minutes later just cleared the crossbar.
That goal seemed to killed off the game as a contest but Beckford managed to force Cech into a good save with 15 minutes remaining as the Leicester players looked to give their travelling support something to remember from the afternoon.
That moment came only moments later when Beckford, who scored on his last appearance at Stamford Bridge, powered home after Danns’ effort had crashed against the post.
The three-goal margin was soon restored through Torres, who scored his second of the game with a near-post header from a Meireles corner with five minutes remaining.
Leicester substitute Marshall then scored arguably the goal of the game as he bent an effort around Cech and into the corner.
Torres showed he has an unselfish side as he passed up the opportunity of a hat-trick to set up Meireles to score low under Schmeichel.