Chocolate Cinnamon Rolls with Vanilla Icing

Name: Chocolate Cinnamon Rolls with Vanilla Icing
Prep time: 1 h 50 min
Cook time: 25 min
Total time: 2 h 15 min
Cuisine: European
Ingredients: 1 egg (medium); 250ml (1 cup) milk; 50g (3 tbsp + 2 tsp) butter; 400-450g (3⅓ -3¾ cups) spelt flour (see note 2); 30g (4 tbsp) cocoa; 40g (¼ cup) brown sugar; 1 tsp vanilla sugar / extract; 7g (2 tsp) dried yeast (see note 3); 1 tsp salt; 75g (⅓ cup) butter (room temperature); 60g (⅓ cup) brown sugar; 20g (1½ tbsp) white sugar; 2 tbsp cinnamon; 30g (1 ounce) milk chocolate (chopped into chunks); 2 tbsp milk; icing sugar (enough to make a thick paste)