Pilot on training flight with flight instructor reported engine malfunction when attempting a go-around which led to landing on the taxiway instead.

Narrative

Practicing for commercial checkride with a CFI and we were doing a steep spiral over the airport. We discussed different aircraft configurations and he suggested doing it with the gear down to achieve a better descent rate. We also discussed doing the spiral and then doing a full stop landing at the termination of it. Upon reaching downwind; still simulating engine failure; I turned an early base; then final; but realizing I was going to be a little too wide on my final turn; I decided to execute a go-around. When I advanced the throttle to go around; the engine sputtered; then seemed to get power before sputtering again. I was over the parallel taxi way at that time (approx 50 ft agl) and with no other traffic in the area; decided to pull the throttle and land straight ahead on the taxiway without further event. After coming to a stop; and assessing what had just happened; I realized that I had forgotten to advance the mixture. This event expressed the necessity to follow ACS (Airman Certification Standards) guidelines for practicing commercial maneuvers. Which should have had us at least 1500 ft agl upon advancing the throttle and ample time to correct the issue and advance the mixture. It also reminds us to follow guidelines from type communities such as the Company on aircraft configurations for executing different maneuvers in different phases of flight. The CFI I was working with did not have a lot of Bonanza specific knowledge and I should have stood on my knowledge of how to operate my aircraft as PIC and followed ABS guidelines and also stuck to only doing maneuvers per the ACS.