Lift the bread pan out of the machine and fit the blade. Put the dough ingredients in the pan, following the order specified in the manual.
Fit the pan into the machine and close the lid. Set to the dough programme.
At the end of the programme turn the dough out on to a floured surface and roll it to a 28 cm (11 inch) square. Sprinkle over three-quarters of the chocolate and the nuts and all of the sugar. Roll up the dough, then put it into a greased 1.8 litre (3 pint) loaf tin. Cover loosely with oiled clingfilm and leave in a warm place for 30 minutes or until the dough reaches just above the top of the tin.
Mix the egg yolk with 1 tablespoon of water and brush it over the dough. Sprinkle over the remaining chocolate and pecan nuts and bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 35—40 minutes until the bread is well risen and deep brown and sounds hollow when tapped with the fingertips. Cover with foil after 10 minutes to prevent the nuts from over-browning.