For the cream cheese frosting
Melt the butter slowly in the microwave or a pan until there are no solids left. Add the liquid butter to a bowl or mixer with half the cream cheese and mix until completely combined, then add the rest of the cream cheese and mix again. Add the vanilla then sift in the icing sugar. Mix for about 1 minute or until smooth, then place the frosting in the fridge until you need it.
For the cake
Grease and line two 25cm (10 inch) round cake tins. Preheat the oven to 150°c. Weigh out all your ingredients; this will save time and help you avoid going wrong. Boil a kettle, cover the chopped dates with boiling water and leave to one side. Blend the peeled clementines to a fairly smooth purée.
Place the oil, sugars, vanilla, salt and eggs in a mixing bowl. Combine with a stand mixer or electric handheld whisk, or beat by hand with a whisk for about 2 minutes, until light and fluffy and fully combined. Add the cinnamon, nutmeg and grated carrot, and mix for about 30 seconds, or until combined. Add your dates, including the liquid they were steeping in, and the blitzed clementines. Mix for a further 1 to 2 minutes, until totally combined. Add all the flour and chopped walnuts, then mix until the flour is fully incorporated which should only take about 30 seconds. Using a spatula, scrape around the bowl, and right to the bottom, to ensure all the flour is combined. Do not over mix the batter once the flour has been added, otherwise your cake will be tough.
Split the mixture between your two tins then pop them into the preheated oven. Cook for 45 to 55 minutes, or when a cocktail stick or skewer comes out clean.
For the decoration
Once your cakes have completely cooled in their tins, turn them out. Place one layer on a cake board, stand, or plate. Frost the first layer, then sprinkle the top with crushed walnuts and finely grate over some orange zest. Carefully place the next layer on top and repeat the process, using plenty of orange zest for garnish on the top.
Store the finished cake in the fridge (because of the cream cheese frosting) for up to 7 days, and remove 1 hour before eating.