Tip the chestnuts into a saucepan with the milk and thyme. Bring to the boil over a medium heat, then reduce the heat to a gentle simmer and cook for 10-15 mins. The chestnuts are ready when they start to fall apart slightly when pricked with a fork.

Meanwhile, heat the butter in a small pan and fry the shallots over a medium heat until softened.

Remove the thyme from the chestnuts and discard. Use a slotted spoon to transfer the chestnuts to a food processor, then pour in 100ml of the poaching milk, reserving the rest. Add the fried shallots and crème fraîche, then blitz to a thick purée, adding more of the reserved poaching milk to loosen if needed. Season with salt and some white pepper to taste. To freeze, leave to cool fully, then seal in an airtight container and freeze for three weeks.

Tip the purée back into the saucepan and cover to keep warm until you’re ready to serve. If the purée needs reheating, add a splash of the reserved poaching milk and warm through over a low heat.