One of the prime goals of the IceCube Neutrino Observatory is to identify tau neutrinos in the astrophysical neutrino flux. The most recent tau neutrino search is based on the high-energy starting event (HESE) sample and has not found any events that could be classified as tau neutrinos. However, this sample rejects all events in the outer detector region to suppress atmospheric background. Given the low expected number of identifiable tau neutrino events it is desirable to combine different suitable event selections in future searches. Here we present an approach where we use an event selection based on a shower-like event signature rather than a fiducial volume veto. This retains events in the outer parts of the detector while greatly reducing background from track-like events. We identify tau neutrino events by means of direct reconstruction of the double cascade topology. Based on Monte Carlo studies, combining this sample and the HESE sample will enhance the number of identifiable tau neutrino events by $\sim$20-45$\%$ for a given observation time at a similar background level.