Coffee Cinnamon Spelt Buns with Coffee Icing

Name: Coffee Cinnamon Spelt Buns with Coffee Icing
Cuisine: European, British
Ingredients: 250ml (1 cup) milk; 1½ tbs instant coffee (see note 1); 50g (3½ tbs) butter; 1 egg (medium); 400-500g (3¾-4 cups) spelt flour (see note 2); 50g (¼ cup) sugar; 7g (2¼ tsp) dried yeast (see note 3); 1 tsp sea salt; 50g (3 tbsp + 2 tsp) butter (very soft); 90g (¼ cup + 3 tbsp) brown sugar; 1 tbs cinnamon; 2 tbsp milk; 2 tsp instant coffee (see note 1); icing / powdered sugar (as much as you need)