The interaction of QCD jets with hot and dense colored matter ("jet quenching") has provided unique experimental probes of the Quark Gluon Plasma, at both RHIC and LHC. However, the full power of jet quenching has yet to be harnessed, because of the difficulty to reconstruct complete jets in the complex environment of high energy nuclear collisions. In this talk I will present a novel experimental approach to jet quenching which enables the first truly infrared and collinear-safe jet reconstruction in heavy ion collisions, and apply it to data from the ALICE experiment at the LHC and the STAR experiment at RHIC.