Having knocked out holders and arch-rivals Real Madrid in the last eight, Barca comfortably disposed of Spain's third-strongest side 3-1 on aggregate as they bid to extend their national record for domestic Spanish Cup triumphs to 26.
Lionel Messi sent Fabregas clear to score the opener in the 16th minute at the Nou Camp, the former Arsenal captain beating his marker to the bouncing ball before lifting it superbly over Valencia goalkeeper Diego Alves.
Valencia had two chances for an equaliser in quick succession at the start of the second half before Alves, who saved a Messi penalty in the first leg, was twice called upon to deny the Argentine with excellent reaction saves.
Valencia's comeback hopes were dashed when midfielder Sofiane Feghouli was dismissed for a second yellow card 13 minutes from time before Xavi ran on to a Fabregas pass and smashed the ball high into the net to make it 2-0 on the night.
"It's been a very long road against some very tough teams but we want to be in all the finals we possibly can," Fabregas said in a television interview.
"It's going to be a great final because Bilbao have some fantastic players and we'll have to be at our best," he added of the title match, the date and location of which have yet to be confirmed by the Spanish football federation (RFEF).
Bilbao, the 23-times winners, ended third-tier Mirandes' fairytale cup run on Tuesday with a 6-2 victory at their San Mames stadium that sent them through 8-3 on aggregate.
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