Good gluten- and nut-free choc cake/brownie recipe?

[phdlife]

My nephew and niece are coeliacs AND my niece is off-the-scale anaphylactic to nuts - but I'd still like to make something choccy for big family bbq we're having soon. Any clues?

ooh yes, I did exact same thing for my godson's christening last week.
it's this Jamie Oliver's party cake adapted as follows:

use doves farm gluten-free flour
leave out the almonds obviously
add an extra egg and 2tsp of baking powder (tesco is gluten-free)

previous thread here with links

thanks chippy

my sister will be even happier if she knows it was a jamie recipe