Take home chocolate cake

Name: Take home chocolate cake
Prep time: 30 min
Cook time: 1 h
Total time: 1 h 30 min
Cuisine: European
Ingredients: 250 gm unsalted butter; 200g dark chocolate (70% cocoa recommended); 1.5 tsp instant coffee granules dissolved in 350 ml boiling water; 250g caster sugar; 2 large eggs; 2 tsp vanilla extract; 240g self-raising flour; 30g cocoa powder plus 1.5 tsp extra for dusting; 1/4 tsp salt; 200g dark chocolate (70% cocoa solids); 200 ml double cream; 1 tbsp golden syrup; 1 tbsp unsalted butter, softened