  Non-local pairing processes at the edge of a two-dimensional topological
insulator in proximity to an $s$-wave superconductor are usually suppressed by
helicity. However, additional proximity of a ferromagnetic insulator can
substantially influence the helical constraint and therefore open a new
conduction channel by allowing for crossed Andreev reflection (CAR) processes.
We show a one-to-one correspondence between CAR and the emergence of
odd-frequency triplet superconductivity. Hence, non-local transport experiments
that identify CAR in helical liquids yield smoking-gun evidence for
unconventional superconductivity. Interestingly, we identify a setup --
composed of a superconductor flanked by two ferromagnetic insulators -- that
allows us to favor CAR over electron cotunneling which is known to be a
difficult but essential task to be able to measure CAR.
