Understanding optical responses of topological matter is central to optoelectronic applications, photocurrent control, and spectroscopy. Yet schemes for sensing ultrafast photocurrents and separating bulk and surface contributions are lacking. We introduce double circular dichroism (DCD) harmonic spectroscopy as an all-optical probe of ultrafast dynamics in topological materials. Pump and probe pulses are circular with independently controlled helicities, yielding the circular dichroism of the circular dichroism: a time-resolved response that evaluates how probe-induced dichroism depends on pump helicity. While DCD vanishes in symmetric systems, it survives in broken time-reversal-symmetry materials, including Chern insulators. Simulations in a Haldane nanoflake, where a pump manipulates chiral current-carrying states and intense probe pulses drive harmonic emission, show that DCD arises from bulk and edge-localized states with opposite signs, similar magnitudes, and different amplitude scaling. Edge-associated DCD is connected to the outermost atomic layer of exponentially localized protected modes and is relatively robust to bulk-edge interference, enabling separation of bulk and edge photocurrents. Varying the electronic structure and laser parameters reveals harmonic anomalies that may probe topological attributes of photocurrents and material phase. In particular, HHG DCD oscillations under band-structure manipulation vary strongly across the phase transition and become stable and nonoscillatory in topologically trivial phases. DCD also oscillates with pump-probe delay on attosecond timescales, offering an ultrafast probe of topological photocurrents and their coherence. DCD could therefore disentangle bulk and boundary photoresponses in broken-symmetry quantum and topological matter and be implemented in photoelectron and absorption pump-probe spectroscopies and chiral systems.