Chestnut soufflé with chocolate & Armagnac sauce

Method

1. Place 250ml of the milk in a medium saucepan and add 50g of golden caster sugar. Place over a low to medium heat and bring to a gentle simmer, stirring to dissolve the sugar.
2. Whisk together all of the egg yolks with a further 50g of the sugar for several minutes until the yolks are pale and fluffy.
3. Remove the milk mixture from the heat and add a few tablespoons to the egg mixture whisking continuously to stop the yolks from cooking. Repeat this several times.
4. Add the egg yolk mixture to the remainder of the hot milk in the saucepan whisking constantly.
5. Return the pan to a low heat and stir constantly with a wooden spoon or spatula, making sure that the contents at the base of the pan are also being stirred. 
6. Keep cooking the custard until it coats the back of a wooden spoon.
7. Strain the custard through a fine mesh sieve and transfer half of the mixture to a clean pan.
8. To the bowl containing the remaining hot custard, add the cream, 1 tablespoon of Armagnac, ¼ teaspoon of vanilla, 2 gratings of the nutmeg and the chopped chocolate. Stir well to combine and until all of the chocolate is melted. 
9. Chill this mixture. It can be kept in the refrigerator for up to 2 days. If it has thickened excessively, add several tablespoons of full cream milk upon reheating.
10. Whisk together the remaining 100ml milk, the plain flour and cornflour until smooth. 
11. Whisk this milk mixture into the custard in the saucepan and place over a medium heat for around 3 minutes, until thickened. 
12. Whisk in the chestnut paste, the remaining Armagnac, vanilla and nutmeg.
13. Preheat the oven to 200°C. 
14. Place the butter in a small saucepan and heat until just melted. 
15. Using a pastry brush generously grease the inside of the ramekins. 
16. Add a tablespoon of caster sugar to each greased ramekin and shake until all the base and sides are thoroughly coated in sugar. Invert and tap to remove any excess.
17. Using a standing mixer or electric whisk, whip the egg whites until they form soft peaks. 
18. Gradually beat in the remaining 25g of sugar a teaspoon at a time, until stiff peaks are formed.
19. Whisk 1/3 of the egg whites into the chestnut mixture. 
20. Fold in the remaining whites in a further 2 additions until thoroughly combined.
21. Spoon the batter into the prepared ramekins and sprinkle ½ teaspoon of sugar on top of each soufflé. 
22. Place the soufflés on a baking tray and bake for 10-13 minutes.
23. Meanwhile, place the custard in a saucepan over low to medium heat and stir regularly.
24. When the soufflés are well risen and firm, remove them from the oven.
25. Using the back of a spoon, push in the centre of each soufflé to create a cavity and fill with the custard sauce.
26. Serve immediately with a marron glacé.