In a small bowl, dissolve yeast in warm water and set aside.
In a large bowl mix milk, sugar, melted butter, salt and egg.
Add 2 cups of flour and mix until smooth. Add yeast mixture. Mix in remaining flour until dough is easy to handle.
Knead dough on a lightly floured surface for 5 to 10 minutes. Place in an oiled bowl, cover and let rise until doubled in size, usually 2 - 3 hours.
Prepare a muffin pan by brushing melted butter all around twelve muffin cups.
Roll out the dough on a floured surface into a 15 by 9-inch rectangle.
Spread melted butter all over the dough. Mix sugar and cinnamon and sprinkle over buttered dough, followed by the chocolate chips.
Beginning at the 15-inch side, roll up the dough and pinch edge together to seal. Cut into 10 - 12 slices.
Place the buns into the muffin cups and let rise until dough is doubled (about 45 minutes to an hour).
For the topping:
Place the chopped chocolate into a medium-sized, heatproof bowl.
In a small saucepan, heat the cream until it just begins to simmer and then pour it over the chopped chocolate. Let it sit a minute, then gently stir with a wooden spoon until the chocolate has fully melted and the ganache is smooth. Then cover and chill until it is set enough to pipe over the muffins.
Bake on 350f/175c for 20 - 30 minutes or until golden brown.
Allow to cool for 5 minutes in the pan before transferring them to a wire cooling rack. Allow to cool 15 more minutes before piping the icing over the buns.