Melt the margarine into the milk (don’t make it more than tepid though)
Place the flour, salt, yeast and caster sugar in a bowl and pour in the warmed milk and margarine mixture.
Bring to a dough and knead until smooth and bounces back when you press a finger onto the surface.
Place in an oiled bowl, cover, and leave to double in size in a warm place.
Meanwhile make the filling: Gently melt together the butter, caster sugar and chocolate. Mix together the vanilla and cornflour. Add the cornflour mix and the cocoa powder to the melted chocolate mixture and stir over the heat until he mixture has thickened a little. Transfer to a bowl, cover and leave to cool.
Preheat the oven to 180 degrees fan
Roll out the dough to a rectangle 20cm wide by 30 cm tall
Spread the filling over the entire rolled out dough, then roll up from the bottom edge until you have a nice tight cylinder. Using a sharp knife or a pizza roller, cut down the length of the cylinder and turn the sides so the cut seam is facing up. Place in a cross formation and then twist each end so you have a twisted rope effect.
Place in a lined loaf tin, cover and leave to rise again for at least an hour.
Bake for 15 minutes at 180 and then lower the temp to 160 for a further 15 minutes.
It will be well risen and golden when done. Then remove from the tin
Make the glaze and brush over the warm loaf