For the carrot marmalade, add the lemon and orange zest and juice to a pan, pour in 500ml/18fl oz water and boil for 10 minutes. Add the carrots, spices and sugar to the pan and cook for approximately half an hour, or until the volume of liquid has reduced to a thick marmalade.
For the candied veg, place the celeriac in a large sous vide bag and add half the sugar. Seal and place in a water bath set at 90C/190F for at least two hours. Repeat the process with the carrots and the remaining sugar in a separate bag. Once cooked, remove the vegetables from their bags. (If you don’t have a vacuum packer or water bath, make a sugar syrup by dissolving the sugar in 500ml/18fl oz water, then cook the vegetables in the sugar syrup over a low heat until tender.)
For the custard and celeriac ice cream, place all ingredients into a bowl and whisk. Half of this mixture will form the base of the celeriac ice cream. Set aside the other half to be used in the bread and butter pudding later.
To make the ice cream, pour half of the custard mixture into a pan and heat over a medium heat until slightly thickened. Do not allow the mixture to boil. It’s ready when the mixture coats the back of a spoon. Once cooked, pour the custard into a bowl and sit that bowl in a larger one filled with ice (alternatively chill in the fridge).
Meanwhile, make the celeriac purée. Place the finely diced celeriac in a pan with the milk and cook until the celeriac breaks down to a pulp. Pulse in a blender until fully smooth and pass through a sieve, if necessary to remove any lumps.
Mix the purée with the cooled custard and pour into an ice cream machine. Churn until frozen following the manufacturer’s instructions and then store in the freezer until ready to serve.
To construct the pudding, place two tablespoons of carrot marmalade into the bottom of eight 7cm/2¾in round heatproof dishes or ramekins. Add two tablespoons of candied celeriac and carrot.
Cut eight round discs of brioche slightly smaller than the dish and 5mm thick. Spread a thin layer of butter on the brioche, then place inside the dishes butter-side up. Cover with the reserved uncooked custard mixture. Leave to rest in a fridge for a minimum of two hours for the brioche to soak up the custard.
Preheat the oven to 110C/225F/Gas ¼.
Place the dishes in a deep oven tray or roasting tin and add enough water to the tray to reach halfway up the sides of the dishes. Bake for 45 minutes or until the custard is set. Once cooked, leave to rest at room temperature.
When ready to serve, sprinkle over some sugar and caramelise using a cook’s blow torch or by placing them under a hot grill. Serve immediately with a scoop of celeriac ice cream.