For the pudding: Break up the chocolate and place in a mixing bowl, add the butter and stand over a pan of simmering water until melted. Remove bowl from the heat and stir until smooth.
Warm the milk in a pan over a low heat then stir gradually into the chocolate and butter mix. Next, add the sugar and stir in.
Beat the egg yolks in a jug and add the vanilla essence. Add to the chocolate mixture, stirring to combine. Mix in the breadcrumbs.
In another bowl, whisk the egg whites. When stiff, fold carefully into the chocolate mixture using a metal spoon.
Turn mixture into a well-greased 900ml pudding mould. Take a large piece of foil, fold a pleat in the middle and us this to cover the dish. Tie string around and loop over the top to make a handle.
Place on a trivet in a large saucepan, pour in enough boiling water to cover the trivet, cover and leave over a medium heat to steam for 1½-2 hours (topping up the water as necessary) until risen and springy to the touch.
Leave to rest for 10 mins or so to allow the pudding to shrink away from the dish sides and then turn out of the mould onto a serving plate.
For the sauce: Break up the chocolate and melt in a mixing bowl over simmering water. Remove from the heat and stir in the golden syrup. Place the cream in a pan and heat gently. When warm, gradually stir into the chocolate mixture. Pour over the pudding to serve.
Recipe by appetite magazine at https://www.appetitemag.co.uk/chocolate-pudding/