Sam2,
You missed the point. Sherry Casks are barrels that used to contain wine. Whiskey makers tayna that it adds to the taste of the whiskey. So you are getting a little wine in your whiskey. A vi veit there is wine in the whiskey and you don’t drink wine the rest of the year, then you are mikayim the minimum according to the Rama if you have have a little more wine then usual and reacdh ad delo yoda.
So you have the little bit of wine and reach ad delo yoda using whiskey.
The joke (and yes this ruins it) is that there is a machlokes haposkim about using sherry casks because of yayin nesech.