Whisk the caster sugar, whole egg and egg yolks together in a bowl. Put the Sheridan’s and the cream in a pan, bring to the boil. Whisk on to the egg mixture, then leave until cooled slightly to make a custard.
Lightly grease six 200ml/7fl oz ramekins with butter, place a layer of croissant slices in the bottom of each one, then add a generous sprinkle of muscovado sugar and a little of the egg custard. Keep on laying up croissant and custard in the same way, finishing it off with a sprinkling of sugar. Allow the pudding to settle for a while to soak up the custard. Heat oven to 200C/fan 180C/gas 6, then cook pudding for 18-20 mins until puffed up, golden and crispy (the muscovado sugar will give a tasty and sticky finish to the pudding).
While the puddings are baking, make the sauce. Place the sugar and butter into a pan and stir over a medium heat until melted together. Pour in the cream and bring to the boil. Reduce the heat and simmer for 3-4 mins until dark and sticky. Serve the puddings in their dishes with a little of the warm butterscotch sauce poured over.