Fudgy Chocolate Brownies

Name: Fudgy Chocolate Brownies
Prep time: 15 min
Cook time: 35 min
Total time: 50 min
Cuisine: American
Ingredients: 90 g good-quality dark chocolate ((at least 70% cocoa solids)); 1/2 cup reduced-salt margarine; 1/2 cup caster (superfine) sugar; 1/2 cup brown sugar; 1 tsp vanilla extract; 2 eggs (and 1 egg yolk, at room temperature, beaten together); 1 cup all-purpose flour; 4 tbsp cocoa powder