It was almost too easy. Antonio Rudiger gave the ball away. Pedri slipped it to Robert Lewandwoski, who then fed an unmarked Gavi. The midfielder's finish was a calm one, threaded into the far corner for a 1-0 lead. His goal was the first of three clinical moves to lift Barca past a languid Real Madrid side, and hand Xavi his first trophy at the helm.
Barcelona had an early chance, with Lewandowski seeing his shot tipped onto the post by a fully-stretched Courtois. And it was a sign of things to come. Gavi opened the scoring, finishing a tidy move off after Rudiger's blunder.
The two switched roles for Barca's second, with Gavi surging forward and squaring for Lewandowski, who couldn't miss from five yards out.
The Blaugrana grabbed a third halfway through the second half, with Gavi involved again. He scampered down the left and found a sprinting Pedri at the back post, who was already celebrating before the ball went into the net.
But as much as the Blaugrana impressed, Madrid produced a miserable showing. Los Blancos didn't register a big chance until the 92nd minute, when Karim Benzema lashed home off a fortunate rebound just inside the six-yard box.
His finish was a mere blemish on an otherwise dominant performance for Barca. They now have their hands on the first domestic trophy of the season, but the final result means much more than that.
Barca are not only deservedly top of the La Liga table, but their latest Clasico performance proves that a changing of the guard is now complete. Carlo Ancelotti's Real Madrid are no longer the best team in Spain - that title now belongs to Xavi's ever-improving outfit.