Stir together the yeast and 125ml/4fl oz lukewarm water in the bowl of a freestanding mixer, fitted with a dough hook. Allow the yeast to dissolve for five minutes.
Add the flour, milk, sugar, melted butter and salt, and mix on medium speed for two minutes.
Remove the dough from the bowl, shape into a ball, wrap in cling film and set aside to rest for 20 minutes.
Dust the work surface lightly with flour. Unwrap the dough and roll into a rectangle roughly 25x38cm/10x15in, cover with a clean tea towel and allow to rise for 30 minutes.
Dot the rectangle with half of the softened butter. Fold the top third of the rectangle down onto the middle, then fold the bottom third up, so the pastry is folded in thirds. Roll out into a rectangle again, fold into thirds again, cover with cling film and place in fridge for 40 minutes.
Remove the dough from the fridge, roll it out to a rectangle as before and dot with the remaining butter. Fold into thirds, roll out again and fold into thirds again. Refrigerate for another 40 minutes.
For the pear and chocolate filling, place the chopped pear in a pan with the sugar. Cook over a medium heat for about 20-30 minutes, or until the pear is soft and sticky.
Roll out the dough, and cut into 12 equal squares, spread the pear onto the top third of each square and top with the chocolate.
Fold the top third of each square over, to enclose the pear and chocolate filling, then roll the filled pastry over onto the lower third. Place seam-side down on two baking trays lined with non-stick baking paper. Cover with cling film and allow to rise for 40 minutes.
Preheat the oven to 200C/400F/Gas 6.
Brush the pastries with the beaten egg and milk mixture and place in the oven for 12-14 minutes, or until golden-brown.
Transfer to a wire rack to cool slightly, then eat warm.