Preheat the oven to 180°C/350°F/gas mark 4 and place a baking tray (sheet) inside to heat up.

Butter 3 ceramic ramekins using a pastry brush, brushing vertically up the sides of the ramekins, as if to help the soufflé rise up. Combine the extra teaspoons of cocoa powder and sugar and coat the bottom and sides of the ramekins with this, tapping out any excess. Set aside.

Sandwich each piece or pieces of chocolate (if they’ve broken more) between 2 halves of a marron glacé.

Fill an ovenproof and flameproof roasting tin (pan), large enough to fit all the ramekins in, with water 2–3cm (¾–1¼in) deep, and put over a medium-high heat until it comes to the boil.

Meanwhile, combine the ricotta, cocoa powder and egg yolks. Separately whisk the egg whites until light and fluffy, then add the muscovado sugar and whisk a little more until just combined. Fold the whisked whites carefully into the ricotta base. Divide the mix between the 3 ramekins. Push the chocolate-filled chestnuts into the centre of each and down to the bottom. Using a palette knife, or a regular knife, run over the top of each soufflé so it has a smooth top, then sweep around the edge of each ramekin with your thumb so that you can just see the rim.

Turn the boiling water off under the roasting tin (pan), place the soufflés in it so that the water comes 2–3cm (¾–1¼in) up the sides of each ramekin, and place on the hot tray in the middle of the oven. Bake for 12–15 minutes, or until risen with a slight wobble, and serve immediately, dusted with icing (confectioners’) sugar, if you like.