How to bake the best ever 12" round dark chocolate cake

How to bake a very moist and very chocolatey 12" round cake.
Ingredients: 650g Unsalted butter or margarine, 650g plain flour, 650g dark chocolate, 950g soft brown sugar, 10 medium eggs, 2 tsp bicarb, 2 tsp baking powder, 100ml dark coffee and 500ml soured cream.
Instructions: Line the side and bottom of a 12" round tin in baking paper.
Wrap three layers of newspaper folded into three to give six layers outside tin. Wet the paper with water .Pre heat oven 160 fan Bake 2 hours 22 mins
Put the chocolate and the butter in saucepan and heat slowly until melted and smooth. Stir in the coffee and leave to cool slightly.
Sift Sugar, flour Baking powder and bicarbonate of soda together in a mixer bowl.
Beat eggs and soured cream together in a jug and pour into the flour mix and mix together.
Add melted chocolate and slowly mix until combined into a smooth batter.
Pour into cake tin.
Bake 2.30 hours. at 160 fan
Do not open oven before 2 hours are up to test.
Leave in tin to cool completely
Unfilled cake will keep for 4 days wrapped in cling film or frozen for a month.