Nigella's Malteser Cake

My boyfriend has been asking for Nigella's Malteser Cake since almost the first time I met him; I've never had it before but he says its amazing. 

I got the recipe here http://www.aspoonfulofsugar.net/wp/2005/01/chocolate-malteser-birthday-cake/ as its from Nigella's Feast book for 2004 which I don't have.  I've read a bit about the cake on other blogs too, most people have said the sponge isn't great so I'm interested to see what its like given it has so little fat in!

Kind of went to town with maltesers on the top...

I've decided that (after 2 large helpings) I don't like cake sponge with only a little fat in, they're weird and chewy and suspiciously springy.  However, I do like the icing so I'll make it again but use a chocolate sponge this time or doctor one slightly to put some Horlicks in and see if that makes it more malty.