Fabulous but easy chocolate cake recipes please

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My parents are coming to visit at the end of this week and dd wants to make her grandma a chocolate birthday cake. I am the worlds worst baker, though I do have good intentions so I want to give it a practice run before thursday which is when the real one needs to be made. Which of course means we all get to scoff lots of chocolate cake all week.
So, any fabulous but simple recipes? I've seen Nigella recommended a few times?

Nigella's cloud cake is really good.

The nigella chocolate and marmalade or jam cake is lovely and foolproof: here. Cherry jam is perfect, though raspberry would be nice.

Take a look at THIS THREAD

the chocolate coca cola cake from Sue Lawrences book of baking is really good. It's the standard chocolate cake in our house and is really easy to do (I couldn't cope with cola bottle sweets on it though)

I was about to recommend the coca-cola cake too. Nigella Lawson has a version too which you should be able to find on her website. It is really easy and very moist.

Here's one I've made up, but it works!

3 eggs separated
180g butter
180g castor sugar
180g plain flour
4 tsp baking powder
180g plain choc melted

Grease and line 2 8"/20cm round tins

Whisk egg whites until stiff
Beat butter and sugar, fold in melted chocolate
Fold in egg yolks
Fold in sifted flour with baking powder, adding a tbsp of milk if needed.
Fold in egg whites gently.

Divide between 2 tins, cook at mark 4 for 20 mins until well-rised and firm

Icing
150g plain chocolate )or double quantities
65g butter )

Melt butter and chocolate together.
Then, either
pour over cake
Or, whisk until thick and paler - milk choc coloured, and then spread over cake. DD refers to this as 'picky cake icing' as she picked holes in it once in the kitchen.

Can make extra to sandwich cakes together, but we prefer lemon curd.

I use this.

Never have any buttermilk in and so substitute the bicarb for baking powder.
The cream ganache is nice but somethimes I just do the cake.

Be warned - it's flipping huge. Takes days to eat it!

Oh and the coffee is a bit unnecessary. I've tried it without and it's better.