  We report a measurement of the half-life of the ${}^{136}$Xe two-neutrino
double beta decay performed with a novel direct background subtraction
technique. The analysis relies on the data collected with the NEXT-White
detector operated with ${}^{136}$Xe-enriched and ${}^{136}$Xe-depleted xenon,
as well as on the topology of double-electron tracks. With a fiducial mass of
only 3.5 kg of Xe, a half-life of
$2.34^{+0.80}_{-0.46}\textrm{(stat)}^{+0.30}_{-0.17}\textrm{(sys)}\times10^{21}~\textrm{yr}$
is derived from the background-subtracted energy spectrum. The presented
technique demonstrates the feasibility of unique background-model-independent
neutrinoless double beta decay searches.
