  We theoretically propose a multidimensional high-harmonic echo spectroscopy
technique which utilizes strong optical fields to resolve coherent electron
dynamics spanning an energy range of multiple electron Volts. Using our
recently developed semi-perturbative approach, we can describe the coherent
valence electron dynamics driven by a sequence of phase-matched and well
separated short few-cycle strong infrared laser pulses. The recombination of
tunnel-ionized electrons by each pulse coherently populates the valence states
of a molecule, which allows for a direct observation of its dynamics via the
high harmonic echo signal. The broad bandwidth of the effective dipole between
valence states originated from the strong-field excitation results in
nontrivial ultra-delayed partial rephasing echo, which is not observed in
standard 2D optical spectroscopic techniques. We demonstrate the results of
simulations for the anionic molecular system and show that the ultrafast
valence electron dynamics can be well captured with femtosecond resolution.
