  The energy-dependence of the anisotropy (the anisotropy energy spectrum) of
the large-scale diffuse gamma-ray background can reveal the presence of
multiple source populations. Annihilating dark matter in the substructure of
the Milky Way halo could give rise to a modulation in the anisotropy energy
spectrum of the diffuse gamma-ray emission measured by Fermi, enabling the
detection of a dark matter signal. We determine the detectability of a
dark-matter-induced modulation for scenarios in which unresolved blazars are
the primary contributor to the measured emission above ~1 GeV and find that in
some scenarios pair-annihilation cross sections of order the value expected for
thermal relic dark matter can produce a detectable feature. We anticipate that
the sensitivity of this technique to specific dark matter models could be
improved by tailored likelihood analysis methods.
