Madrid trailed, 3-2, from the first leg, but took advantage of some catastrophic defending from Barca to score twice early on and squeeze the game out—winning the tie, 4-4, on the away-goals rule.
Goals from Gonzalo Higuain and Cristiano Ronaldo arrived inside the opening 20 minutes for Madrid, with the first the result of a miskick from Javier Mascherano that sent Higuain clean through on Victor Valdes.
The second owed to Ronaldo's extravagant flick over Gerard Pique's head, which presented a chance for the Portuguese to stamp his name on yet another Clasico. Ronaldo took it with aplomb.
With Madrid up 2-0 inside 20 minutes and rampant, Barca looked as vulnerable as we've seen them in recent memory. And when Adriano was sent off for pulling down Ronaldo just shy of the half-hour mark, Tito Vilanova's team appeared on course for humiliation.
It was time for Valdes to earn his money. First, he saved from Higuain and then Sami Khedira. And then, Mascherano went some way to redeeming his earlier mistake with a desperate goal-saving tackle to deny Higuain again.
Barcelona were clinging on. All the while it stayed at 2-0, they were still in touch, and when Lionel Messi—who else?—curled a free kick past Iker Casillas at the stroke of halftime, you began to wonder if Madrid were about to be reeled in.
Seconds later, Higuain shot wide with the goal at his mercy. Another chance went begging. More doubts crept in.
From there, it was Barca who took control—belying their one-man disadvantage to set about doing what they do best. The passes started the flow, and Barca started to believe. Madrid appeared to be doing the opposite.
At 62 minutes, Mascherano played a defense-splitting pass to Pedro, and the winger would have scored but for a fine save from Casillas.
Chances followed for both sides in the remaining half hour, but neither took advantage. It was Barca who had the better of things in the second half, though, and Vilanova will at least emerge from the contest knowing his team will put up a fight for him.
Mourinho has something more tangible to grasp at—the first trophy of the season in Spain. And with it, the first scalp in his battle with the new man on the other side of club football's best rivalry.
Madrid fans will be hoping a Clasico triumph is exactly the fillip they needed to kick-start their season.