Veg scheme member Pam suggests adding lemon or orange juice to the mix, to make the cake deliciously moist.
Grease a square cake tin. Line it with greaseproof paper, then grease lightly again.
Preheat the oven to 180C/Gas 4.
In a large mixing bowl, whisk the eggs, then mix in the oil, sugar, lemon zest and grated parsnips.
Over a second large bowl, sift the self-raising flour, baking powder, cinnamon and salt. Make a well in the centre, then pour in the parsnip mixture. Add the chopped walnuts (save a handful to scatter over the finished cake if you like) and stir to make a stiff batter. Pour the mixture into the prepared cake tin, spreading it out evenly.
Bake for 60 to 80 minutes or until the cake is well risen, the top is firm, and a metal skewer inserted in the middle comes out clean.
Allow the cake to cool for 5-10 minutes in the tin before lifting it out to a wire rack to cool completely.
To make the icing, mix the cheese with the lemon juice and add icing sugar to taste. Spread over cake when completely cool and scatter over the remaining walnut pieces.
300g parsnips, peeled and grated
2 eggs
125ml sunflower or coconut oil
200g caster sugar
zest of 1 large lemon, finely grated
350g self-raising flour
1/2 tsp baking powder
1 tsp cinnamon
1/2 tsp salt
50g walnuts, chopped
For the icing:
150g cream cheese
2 tsp fresh lemon juice (use the one you zested above)
icing sugar