Step 1: bake two half spheres of cake (I cheated and bought a half sphere mould).
Spend a long time trying to work out why it takes twice as long to bake as the recipe said it would (I still haven't worked out an answer to that!
Step 2: create some grey royal icing - buy royal icing, keep adding black food dye until it's a particularly unappealing grey colour
Step 3: create lots of butter cream icing. Sandwich two halves of cake together, cover the outside in the remainder of the icing
Step 4: roll out icing, wonder how on earth you're going to move something that big and prone to stretching/breaking. Somehow manage it by draping over rolling pin, drop on to cake and hope for the best.
Step 5: Do your best to smooth royal icing round a (kinda) sphere, a shape that is not meant to be iced. Suddenly realise you can't remember what a Death star looks like, google death star, realise there's no hope because you're definitely not that artistic. Stick additional bits of icing on in attempt to make ball of grey look like death star. Consider using lego men to make it look more star warsy. Try to make a Millennium Falcon out of icing as another clue, fail, give up!
Step 6: Stick the candles in the top and hope for the best!
He worked out what it was meant to be, so I'm basically happy with the outcome, and it tasted a lot better than I expected it to considered how long it was in the oven for!