  We propose a new search for Dark Matter at the LHC, characteristic of
scenarios beyond the Standard Model with a pseudoscalar portal between the
visible and dark sectors. This search, leading to a $\bar{b} b Z( \rightarrow
\ell\ell) + E_{T} \hspace{-4mm}/\hspace{2mm}$ final state, reaches large
regions of parameter space not probed by Dark Matter searches via multi-jet $+
E_{T} \hspace{-4mm}/\hspace{2mm}$, searches for new scalars and flavour bounds.
We show that this search could be used to test the Dark Matter origin of the
gamma ray Galactic Centre excess with LHC Run 2 data.
