  Measurements of inclusive hadron suppression and di-hadron azimuthal
correlations in ultra-relativistic nuclear collisions at RHIC have provided
important insights into jet quenching in hot QCD matter, but are limited in
their sensitivity due to well-known biases. Full jet reconstruction in
heavy-ion collisions would conceptually provide a direct measurement of the
energy of the scattered parton before energy loss, alleviating such biases and
allowing a measurement of the energy loss probability distribution in a
model-independent way from hard probes. In these proceedings we utilize recent
progress in the reconstruction of jets in the heavy ion environment and present
the first measurement of the fragmentation function from fully reconstructed
jets in heavy ion collisions. The fragmentation function measured in central
Au+Au collisions at $\sqrt{s_{_{\rm NN}}}=200$ GeV will be presented and
discussed with respect to p+p reference measurements.
