Prepare the filling. Grind the nuts to a fine powder in a food processor. Gently warm the Stork, evaporated milk and caster sugar in a small pan until melted and combined. Stir in the ground nuts and cocoa powder. Heat gently, stirring well until the mixture thickens. Remove from the heat and transfer to a bowl to cool to room temperature.
To make the dough combine the flour, sugar, yeast, salt, soured cream, eggs and melted stork. Mix to a rough dough. Knead the very soft dough in the bowl for 10 minutes, pinching the dough with your fingertips, lifting and pressing back down. Transfer to a lightly greased bowl, cover and allow to rise for 1 hour.
Lightly grease the worksurface and split the dough in half. Roll out each portion to a rectangle approx. 25cm x 40cm. Spread with half of the cooled filling and scatter with half of the choc chips. Fold over the two short edges just a little to encase the filling and roll the dough from the long edge tightly to make a long roll. Pinch together the dough at the seam.
Transfer to a well greased or lined baking tray, cover loosely and allow to rise for 3 hours. Brush well with milk and bake (160c (fan)/180c/Gas Mark 4) in the oven for 35 minutes until golden.