Easy Chocolate Cake

Sponge

• 120 g caster sugar
• 120 g self-raising flour
• 30 g cocoa powder
• 120 g sunflower oil, plus extra for greasing
• 100 g whole milk
• 1 tsp baking powder
• 1 tsp vanilla extract
• 2 large eggs

Icing

• 125 g dark chocolate (70% cocoa solids), small pieces or callets
• 125 g sour cream