Vegemite is a very individual thing: toast [seedy/grain, lightly toasted] needs to be warm, definitely butter, not marg ~ & spread thin; very thin. With coffee.I disagree with the Jackman method.
For me it's wholemeal seedy bread, lightly toasted, cooled (that's always the most contentious part of the MJ method), thick butter-not-marge, thin vegemite. Paired with a cup of tea. Perfect.
