(Corrects to three penalties in paragraph 13)By Fernando KallasMADRID :Barcelona's Robert Lewandowski scored a quick-fire second-half double to set the leaders on course for a 4-0 thrashing of Real Madrid that handed the hosts their first defeat in 42 LaLiga games in a sensational Clasico encounter on Saturday.The Polish striker pounced with two goals in three minutes early in the second half before Lamine Yamal at 17 years and 106 days old became the youngest Clasico scorer and captain Raphinha wrapped up a comfortable win late on at a stunned Bernabeu.Barca stretched their lead at the top with 30 points, six above Real who saw their unbeaten LaLiga run come to a bitter end after 13 months, leaving them one tantalising positive result away from equalling the Catalans' league record of 43.After four consecutive Clasico defeats, Barcelona claimed their first triumph over Real since March 2023 in style with a clinical performance in which they were true to coach Hansi Flick's ideas of gambling with an aggressively high defence.The visitors were more than comfortable playing on the counter-attack, exploiting the lightning speed of Raphinha and Yamal to help feed LaLiga top scorer Lewandowski.Real were on top at the start but became frustrated as they wasted several chances, mainly through off form Kylian Mbappe who missed four clear opening from close-range and was caught offside nine times, including having two goals ruled out.Despite Real dominating proceedings, Barca kept playing their risk-taking tactics and the gamble paid off when Lewandowski silenced the crowd with a two-goal blitz in the 54th and 56th minutes to reach 14 goals in 11 league games.