Rahul's Edible Rock Garden Chocolate Cake recipe - The Great British Bake Off

Ingredients

• 100g cocoa powder
• 120ml boiling water
• 600g dark brown soft sugar
• 200g baking margarine or softened salted butter
• 6 eggs
• 350g self-raising flour
• 2 tsp baking powder
• 200g caster sugar
• 4 egg whites
• 250g salted butter, diced
• 250g unsalted butter, diced
• 1 tsp orange extract
• 1 tsp vanilla extract
• 1 tsp lemon extract
• green and red food-colouring gels or pastes
• 100g caster sugar
• 75g 70% dark chocolate, roughly chopped