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Place the chopped parsnips and milk in a saucepan over a medium heat. Bring to a simmer and cook until soft. Drain, reserving 125ml of the milk. Spread the parsnips out on a tray so that the excess moisture evaporates.
When dry, purée the parsnips until smooth, then place in a kitchen towel or piece of muslin and squeeze out any remaining moisture.
Place the reserved milk in a saucepan and bring to the boil, taking care not to let it boil over. In a mixing bow, beat together the egg yolks, sugar and glucose. When the milk has boiled, pour it immediately over the yolk mixture and stir to combine.
Place the crème fraiche in a large stainless steel bowl and set aside.
Return the custard mixture to a clean saucepan and cook slowly over a low heat until it thickens slightly. Do not let the mixture boil or simmer or it will separate, in which case you will have to start over again.
When the custard has thickened enough to coat the back of a spoon, pour it over the crème fraiche and mix well. Add the parsnip purée, stir until combined, then churn the mixture in an ice cream machine until firm enough to scoop.
Transfer to a clean container and store in the freezer.
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