Preheat the oven to 175ºC/350ºF/Gas mark 4 and grease a pair of 23cm/9-inch circular loose-bottomed cake tins

In a medium-sized mixing bowl, sift together the flour with the ground spices, baking powder, bicarbonate soda and salt

In a large mixing bowl, add the grated sweet potato, vegetable oil and sugar and combine

In a measuring jug lightly whisk the eggs before adding the vanilla extract. Stir to mix in

Stir in the egg mixture to the sweet potato in 3 batches, stirring well after each addition

Carefully fold the flour mixture into the sweet potato mixture

Add the chopped walnuts and stir in so they're well dispersed through the batter

Pour the batter equally between the two cake tins before baking for 20 minutes in the centre of the oven

After the 20 minutes, turn the oven down to 150ºC/300ºF/Gas mark 2 and cook for a further 10 minutes or until a skewer inserted into the middle of a cake come out clean

Allow to cool on a wire rack for 15 minutes before taking the cakes out of their tins

Allow to cool completely (at least another hour). Make the frosting.

Mix the cream cheese and softened butter until there are no lumps

Add the vanilla essence and icing sugar (sieve the sugar first if there are any lumps) and mix thoroughly. Cover with clingfilm and store in the fridge until the cakes have cooled and are ready to frost

Once cooled, turn one of the cakes over so that the top is face down on a serving plate. Cover the top generously with frosting.

Place the second cake on the first, with the top facing up. Cover the top generously with frosting. Serve. The cake will keep for up to 5 days in the fridge.