Are the two the same? I want to try the chocolate mud cake recipe and it calls for self raising flour and castor sugar. Is this just a difference in language or are they different than American products?
Self-rising flour and Self-raising flour are the same thing.
Caster (castor)/superfine sugar is granulated white sugar that has superfine granules and is good for making meringues as it dissolves rapidly. You can make your own by processing granulated sugar in your food processor for a few seconds.