6-inch Dense Spelt Chocolate Fudge Cake

Name: 6-inch Dense Spelt Chocolate Fudge Cake
Cuisine: American
Ingredients: 50g (1¾ oz) milk chocolate (chopped); 85g (6 tbsp) butter; 90g (½ cup) dark brown sugar; 1 large egg + 1 egg yolk; 1 tsp vanilla extract; 60g (½ cup) white spelt flour (see note 1); 25g (¼ cup) cocoa powder; 30ml (2 tbsp) milk; ½ tbsp instant coffee (dissolved in the milk); pinch salt; 100g (7 tbsp) butter; 40g (⅓ cup) cocoa powder; 150g (1¼ cups) icing sugar (sifted); 2-4 tbsp milk