This will keep for up to a month in the freezer. Defrost it and serve it at room temperature, scattered with fresh thyme leaves.
23cm-diameter tart-dish, 300g of shortcrust pastry, 100ml of cream, one and a half kilos of Jerusalem artichokes (scrubbed but not peeled, six cloves of garlic (crushed), 25g of flour, 25g of butter, four eggs, one and a half teaspoonfuls of salt, one tablespoonful of fresh thyme leaves.
Preheat the oven to gas mark 5/190C. Boil the Jerusalem artichokes until they are tender, then drain them and slice five of them, setting them aside. Purée the remainder of the artichokes until smooth, with the flour, butter, eggs, cream, salt, garlic and thyme. Roll out the pastry and use it to line the tart-dish, trimming off the ends. Pour in the filling and top it with the sliced artichokes. Bake this for 45 minutes. Freeze it once it has cooled.