Preheat your oven to 180 C/ 160 C fan and grease and line two 8 inch cake tins.
Mix the flour, baking powder, bicarbonate of soda, spices and salt together in a medium sized bowl.
Add the sugar and stir until combined, breaking up any lumps with your fingertips.
Add the eggs and oil to the dry mixture and beat well.
Fold in the juice pulp, sultanas, hemp seeds and mixed nuts, adding enough fresh juice to make a soft batter consistency.
Spoon the mixture evenly into the prepared baking tins and bake for 30-35 minutes. Transfer to a wire rack to cool completely before unmoulding.
To prepare the frosting, cream together the butter, icing sugar and vanilla until light and fluffy. Gently fold in the cream cheese until combined.
Using a palette knife, spread 1/3 of the frosting over the top of one cooled cake, top with the other cake and spread the remaining frosting over the top (and sides, if you want). Sprinkle with a few chopped nuts for decoration.