In a large measuring jug, stir together the milk, sugar, and yeast. Set aside and allow the yeast to foam and bubble up - about 10 minutes.

In a large mixing bowl, add the milk mixture, butter, eggs, and yolk, and whisk until combined.

Add the flour, cocoa powder, and salt, and mix until a sticky dough forms.

Transfer the dough to a lightly floured surface and knead for about 5 minutes until smooth, elastic, and tacky. Your hand will stick to the dough when kneading, but should come off completely clean.

Place the dough into a lightly greased large bowl, cover with clingfilm or a tea towel, and leave to rise in a warm place for 1 - 2 hours, or until doubled in size.

In a medium mixing bowl, mix together the butter, sugar, and cinnamon until combined. Set aside.

Once the dough has doubled in size, gently deflate with your fist and transfer to a well floured surface.

Roll out to a large rectangle, about 1/4-inch thick, making sure the long side is facing towards you. Slice off the edges to make a 12 x 18 inch rectangle.

Spread the filling all over the dough, then sprinkle on the chocolate chips.

Using a pizza cutter, cut the dough into twelve 1.5-inch-wide strips. Roll up each strip and place them into a greased 9x13-inch baking pan.

Cover with clingfilm or a tea towel, and leave to rise again in a warm place for 30 minutes.

Preheat the oven to 180C/160C Fan/350F/Gas 4.

Remove the clingfilm/tea towel and bake the rolls for 30 - 35 minutes, or until the internal temperature of the rolls reach 88C - 93C (190F - 200F).

Allow to cool in the pan on a wire rack whilst preparing the topping.

In a medium mixing bowl, mix together the cream cheese and butter until combined.

Add the icing sugar, cocoa powder, and vanilla, and mix until smooth and combined.

Spread the icing over the cinnamon rolls. Serve warm and enjoy!