Slice the brioche loaf into thin slices and cut each slice into two triangles.
Place the milk and double cream and saffron if you are using it, into a heavy based pan and slowly bring to the boil.
Once boiled, take it off the heat and allow to cool slightly.
Whisk the eggs and the sugar together until it is pale, light and leaves a trail.
Add the cooled cream and milk to the egg mixture and whisk together.
Butter a baking dish with the 30g of softened butter and arrange all the brioche triangles into it.
Scatter the golden raisins on top of the bread and carefully pour on the custard.
If any of the bread floats to the top, push it down with the back of a spoon, ensuring it is immersed in the liquid.
Chop the pistachio nuts into thin slivers and scatter over the pudding.
Leave the pudding for several hours or overnight to ensure that the bread has soaked up all the liquid.
Place the baking dish into a larger roasting tin, which has been lined with a newspaper. Fill the roasting tin with warm water so the water comes up half way up the side of the baking dish. This is a bain-marie, or a water bath and will prevent the milk from boiling and curdling the eggs.
Place into the oven and cook in a pre-heated fan-assisted oven at 165 degrees celsius or equivalent, for 35-40 minutes, or until the top is golden brown, but there will still be a slight wobble.
Serve hot or cold.
Tips
If you do wish to make this dessert gluten free, use gluten free brioche rolls, slice and follow the instructions.
If you do not have vanilla sugar, just use regular caster sugar.
If you want to make vanilla sugar, add a vanilla pod into a container of caster sugar. Store and use as required.
It is best to use golden raisins, or even green raisins if you wish.
Using saffron is optional. It will change the flavour of the custard and will add a mellow yellow tinge to it.