I attempt to gank from a battlefield to another battlefield but I am stunned. Do I get recalled to base or to my original battlefield?

You are recalled to your base.

According to Rule 450 and the official clarifications on Recall, a recall is defined as relocating a permanent from anywhere to its base. Regardless of whether you were stunned or where you were moving from, a recall always sends units to the base, not to their previous battlefield location.

This is further supported by the RiftJudge FAQ #7062:

"Ruling: Recall always sends units to the base, not to their previous battlefield location."