With regards to isomerizing with KOH, you could follow the quantities/methods used for isomerization of Safrole on Rhodium's page. Experimentation will be necessary in order to determine the time required for most of the asarone to become the trans isomer.
With regard to the KOH, recrystallization will remove this if any remains dissolved post-reflux.
Have a look at: https://www.thevespiary.org/rhodium/Rhodium/chemistry/isomerizafrole.html (https://www.thevespiary.org/rhodium/Rhodium/chemistry/isomerizafrole.html)
One more thing, I am not sure whether cis to trans conversion is as rapid with ethanolic KOH as with KOH in neat oil.
This is a technique that needs to be experimented with in order to assess its utility.