Prepare the matcha and vanilla creams in two separate bowls, using electric mixers.For making matcha ice cream, mix the heavy whipping cream until soft peaks form. Add in matcha powder, salt, erythritol, and vodka (optional), and mix until stiff. Split a vanilla bean lengthwise using a sharp knife and scrape out the vanilla seeds. For making vanilla ice cream, mix the heavy whipping cream until soft peaks form. Add in vanilla seeds, salt, erythritol, and vodka (optional), and mix until stiff.