Preheat the oven to 340°F / 170°C. Grease a loaf pan and line with baking parchment.
Peel and grate the raw parsnip and set aside.
In a large bowl, cream the butter and sugar together with an electric mixer (or vigorously by hand) until light and fluffy.
And the eggs one at a time and beat each one in well.
Mix in the parsnip and then sift in the flour and baking powder and combine. Add the milk and gently stir to combine.
Pour the mixture into the prepared loaf pan and bake for 60 minutes or until an inserted skewer comes out clean. If the cake is browning too quickly, cover it with foil loosely.
Cool the cake in the pan for 15 minutes and then remove from the tin and allow to cool completely.
This cake lasts well, covered, for up to four days.