Preheat oven to 180 C / Gas 4. Grease an ovenproof dish.
Put the butter, sugar and treacle in a pan and heat till boiling. Allow to boil (don't stir) for 4 to 5 minutes to form a toffee sauce.
In another pan, warm the cream (don't allow to boil).
Cut or rip your bread in chunks, then mix into the warmed cream. Place a layer of the bread in the bottom of the pan. Pour some of the toffee sauce over, then add another layer of bread, then toffee sauce until finished.
Bake 18 to 20 minutes until golden.
If you only have dark brown sugar to hand, use that but substitute golden syrup for the treacle to balance out the flavours!