The Barossa Valley has two local cheesemakers, three local bakeries and almost-local butter, so you really have to use local ingredients.

Ballycroft Fresh cheese
Apex 1918 wholemeal bread
Paris Creek B-D butter

Now for a bit of added flavor, I like
fresh dill
or
horseradish (ground from your own roots and blended with local Kurianda wine vinegar)

Assemble, brown it up, and enjoy.