Preheat the oven to 100C/225F/ Gas ¼.
Heat the cream and milk in a saucepan until hot, but not boiling.
Whisk together the eggs and egg yolks with the sugar in a mixing bowl.
Slowly pour the heated milk and cream into the beaten egg mixture, whisking continuously. Set aside.
For the toffee sauce, melt the sugar in a pan over a medium heat and cook until it goes a caramel brown.
Stir in the butter and cream (it will bubble furiously, so be careful as you stir) and stir continuously until smooth and completely incorporated.
Coat the bottom of a greaseproof dish with a third of the caramel sauce.
Top with a layer of the brioche slices and then pour over a third of the custard ensuring it fully coats all the brioche pieces. Repeat the process until you have three layers.
Bake in the oven for one and a half hours or until golden-brown and set.
Serve the pudding with a good-quality ice cream.