Raul Meireles opened the scoring before the Spaniard grabbed his first and second Champions League goals for the west Londoners, with Branislav Ivanovic and Salomon Kalou completing the rout.
Chelsea went into the game with a changed line-up but never looked troubled by their Group E opponents.
Torres, who is currently serving a domestic ban, is slowly beginning to show glimpses of his finest form and he hit post in the opening few minutes of the game.
But it was who Meireles put the Blues ahead after he was left with too much space in midfield and fired in from 25-yards to net his first goal for the club.
Torres added his name to the score-sheet moments later when he was found in space by Frank Lampard and coolly slotted the ball past Genk goalkeeper LÃ¡szlÃ³ KÃ¶teles to double the home sideâ€™s lead.
The last time the Chelsea No9 had scored in the competition was against his current employers over two years ago.
And the former Liverpool duo combined to kill the game off just before the half-hour mark.
Meireles lofted in a perfectly aimed cross, which Torres met with a glancing header to double his tally for the evening.
Chelsea centre-half Ivanovic then put the game beyond doubt just before half-time when he headed in a Florent Malouda free-kick to net his first goal of the season.
Genk midfielder Kevin de Bruyne, who was a summer target for the Blues, was the Belgian outfitâ€™s only real threat as they endured a torrid evening in west London.
The second-half sprung into with life when Chelsea grabbed their fifth of the night in the 73rd minute.
Torres was involved again and nearly grabbed his hat-trick as he connected with a JosÃ© Bosingwa cross, but Koteles saved from point-blank range.
However, the ball fell to second-half substitute Kalou, who volleyed home to cap an impressive display as Chelsea extended their perfect record against Belgian opposition and maintained their position at the top of Group E.
Chelsea: Petr Cech, David Luiz, Ashley Cole (Paulo Ferreira, 45), Branislav Ivanovic, JosÃ© Bosingwa (Alex, 78), Raul Meireles, Frank Lampard (Salomon Kalou, 68), Oriol Romeu, Florent Malouda, Fernando Torres, Nicolas Anelka.
Genk: LÃ¡szlÃ³ KÃ¶teles, Anele Ngongca, Daniel Pudil, Abel Masuero (Fabien Camus, 45), Khaleem Hyland, Anthony Vanden Borre, Thomas Buffel, Kevin De Bruyne, Daniel TÃ¶zsÃ©r, Elianiv Barda (Dugary Ndabashinze, 71), Jelle Vossen (Kennedy Nwanganga, 81).
“It was very good display by the team, very focused. The boys kept going through the first half fantastically well, keeping the rhythm high.
“In the second half we missed a couple of passes but increased the tempo in the last 10 minutes, which was good. It was a good result and puts us in a good position for the last three games.”
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