Make the dough: In a small pot melt the butter. Take off the heat and stir in the milk and sugar. Add 1 egg + 1 egg yolk (save the white in the fridge for glazing the buns) and stir together.
In a large bowl mix the flour, salt and yeast - make a well in the centre of it. Pour in the butter mixture and stir together to make a soft dough.
Tip out onto a floured work surface and knead gently for about 6 minutes, dusting with flour as needed, until the dough is smooth and less sticky. Oil the large bowl you used and place the dough into it. Cover with clingfilm and leave in a warm place to rise for 1 1/2 hours.
Now make the filling: melt together all the filling ingredients (except the pecans) over a low heat in a small saucepan, stirring constantly to prevent burning. Remove the mixture from the heat and set aside at room temperature to cool as the dough continues to rise.
Once the dough is risen tip it out onto a floured surface. Dust it with more flour and gently roll it out into a roughly 25 x 35 cm rectangle.
Transfer the rectangle of dough to a floured cookie tray. Cover the entire surface with a thick layer of the chocolate mixture (it should be pourable but not super runny - if too thick, gently warm it up a bit. If too thin, put it in the fridge to cool for a bit) and sprinkle with the chopped pecans. Place the tray into the fridge for 10 minutes so that the filling can firm up.
Remove the tray from the fridge and fold the dough into thirds like a business letter so you end up with a roughly 25 x 10 cm rectangle. Cut the dough into six (25 cm long) strips. Twist each strip along its length and then coil it up (see .gifs at above recipe)(this doesn't need to be precise!).Line the baking tray with baking paper and place the buns onto it. Cover loosely with oiled cling film and leave in a warm place to prove for an hour.
Preheat the oven to 180 C. Remove the cling film from the buns. Take the egg white which was leftover from making the dough and whisk 1 tbsp of water into it with a fork - use this to glaze the buns with a pastry brush.
Bake the buns for 17-20 minutes, until dark golden-brown.
Eat warm or leave to cool on the tray before storing in an airtight container at room temp.