Grease and line the base and sides of a 6" (15cm) round baking tin, preferably a deep one. If it isn't so deep just line the sides tall (with extra parchment that overlaps the sides in order to give it a tall look).

Place the yeast in a small deep bowl, add about 2 tablespoons tablespoons of water and 1 teaspoon of sugar. Cover with cling wrap or a lid and keep in a warm place till the yeast froths up, about 10 minutes. If the mixture doesn't look frothy, the yeast is old and useless. Discard it and start again with a new package of yeast.

Sift the flour, cocoa powder and salt together into a large bowl and mix in the caster sugar. Make a well in the centre and pour the yeast mixture into it and gradually knead the mixture into a dough

Tip the dough onto a lightly floured surface and knead the butter into it gradually until the dough is soft and pliable. Place the dough ball into a lightly oiled bowl and turn it over gently till it is well coated with the oil. Cover with a cling wrap and leave it in a warm place to double, anywhere between 1-2 hours depending on the weather. You can leave it in an oven with the light on.

Once the dough has doubled, turn it onto a working surface and lightly punch the air out. Knead in the chopped chocolate (preferably let the chocolate remain in the centre, so don't over knead or it will spread over the entire dough). Cover with cling wrap and let it rest for 5 minutes

Shape the dough into a round and place it in the prepared baking tin and cover it again with the cling wrap. Let it rise for another 45 minutes to 1 hour or until risen to the top of the tin/overlapping baking parchment.

Preheat oven to 220 C and bake the bread for 10 minutes. Reduce heat to 190 C and bake for another 25-30 mins. Remove and brush the top with the melted butter. Let it cool completely on a wire rack. Slice and serve with butter, jam/marmalade or nutella.