Surprisingly, there only seem to be two recipes for these in general use. One based on an Emeril Lagasse recipe, and the one I used, found here, which I chose over the Emeril recipe because it melts a large proportion of the white chocolate into the cake batter. Some variations of this second recipe use more butter. I baked in an 8" square tin, and got a tray of blondies of a reasonable depth, which could be cut into 16 pieces.
The texture was much better than those of the Butterscotch Blondies which I made earlier in the week, but my Chief Tester thought they were lacking in any defined flavour, other than vanilla, and I think I agree with him. Even the macadamia nuts, although they added a good crunch to the texture, lost their flavour in the overwhelming vanilla blandness.
He much preferred the flavour of the Butterscotch Blondies, so I am now on a quest for something with the texture of these but the flavour of a blondie made with brown sugar. I may have to do some experimenting with amalgamated recipes, unless anyone has any suggestions.