An electric opening 30 minutes in which Xavi and Lionel Messi scored either side of a Pedro double was enough to secure victory for Tito Vilanova's men against their city rivals
A sublime opening half hour from Barca did all the damage, with Xavi opening the scoring after just 10 minutes. Pedro soon netted a double before Lionel Messi slid home from the spot, after Cesc Fabregas had been brought down in the area.
The winter break proved unable to disrupt the Blaugrana's typically flowing football as they took command of the game from the first second, seemingly buoyed by the return of Tito Vilanova to the bench after surgery.
Operating from the left, Andres Iniesta was dancing past the Espanyol defence with ease and it only took 10 minutes for him to create the opening goal. Having been picked out in space by Messi, Iniesta drilled a low cross into the area which Xavi coolly slotted home unmarked.
The hosts were unrelenting and after Kiko Casilla made a great save to keep out Iniesta in the 13th minute, it took just another couple of minutes for the second to come.
Cesc displayed great balance as he dribbled past Javi Lopez before cutting the ball back to Messi. The Argentine flicked it into the path of Pedro, who managed to make enough of a connection to send the ball into the far corner.
Midway through the half Sergio Garcia blazed a golden chance to halve the deficit over the bar, and it proved costly, as Pedro added Barcelona's third in the 27th minute. Busquets' perfectly-weighted through-ball was tucked away by the winger with a delightful first-time dink over the keeper.
It went from bad to worse for Javier Aguirre's men as Casilla was ajudged to have illegaly brought down Cesc inside the area just two minutes later. Messi was given the responsibility of the spot-kick and he nonchalantly slotted in his 27th Liga goal of the season.
The rampant Catalan giants soon stepped off the gas, though, and cruised into the break with the game already won.
But the second half did not bring about a change in the pattern of the game as Barca continued to retain the ball, forcing the Periquitos to chase shadows.
The cutting, clinical nature of the hosts had ebbed in the second half but Pedro can count himself unlucky not to have bagged his hat-trick as he twice had the ball in the net again, only to see the goals chalked off for debatable offside decisions.
Espanyol almost grabbed a consolation goal as Juan Angel Albin pounced on a short pass back to Valdes by Gerard Pique, but the Uruguayan could not find a way past Victor Valdes.
The humiliation was almost compounded in the 82nd minute as Messi struck a fantastic 30-yard free kick at goal but the crossbar saved the flailing Casilla.
Victory moves Barcelona 12 points clear at the top of the table, though that lead could be reduced back to nine should Atletico Madrid defeat Mallorca later in the evening.