You can make either the 8" or 6" cake first, the instructions are the same for both, or make both cakes at the same time if you have enough oven space!
Pre-heat your oven to 160C Fan/180C/350F/Gas Mark 4, and grease and line two 8" cake tins, and two 6" cake tins (that are at least 2" deep)
Place the dates and boiling water into a bowl and leave them to soak for 15 minutes
Puree the dates and water together using a stick blender or food processor
In a large mixing bowl, weigh out the self raising flour, wholemeal flour, baking powder and cinnamon
In a second mixing bowl, whisk the eggs, vegetable oil, milk and date puree together. Add the mashed bananas and mix in
Add the grated apple and mix in
Pour the banana/egg mixture into the bowl of flour, and mix until combined
Divide the mixture between the tins, using scales for accuracy if you like
Bake the 8" cake for 40-45 minutes or until a thin skewer inserted in the centre comes out clean. Bake the 6" cake for 25-30 minutes or until a thin skewer inserted in the centre comes out clean. Leave to cool fully
To make the cream cheese frosting mix together the butter and cream cheese until combined, then stir in the vanilla extract and agave nectar
Use a cake leveller or a knife to level off the cakes if they have domed at all, or the top of them is not flat
Place the first 8" cake layer onto a cake board, plate or cake stand
Spread cream cheese frosting over the top of the cake, then add the second 8" cake layer and cover the whole cake with the frosting
If you are adding the 6" tier, you will need to support the cake with dowels. This stops the cake from collapsing. Roughly mark out a 6" sized cirle on top of the cake. I usually hover a cake tin over it and mark a dent in the frosting using a butter knife. Then insert three evenly spaced out dowels into the cake, inside the marked circle. You will need to cut the dowels to size
Place the bottom layer of the 6" cake onto a 6" cake board and spread the top with frosting, then add the top layer. Place the whole 6" cake on top of the 8" cake
Cover the entire 6" cake in cream cheese frosting, making sure to cover the join between the tiers
Add berries of your choice. Please note that berries will run their juice into the frosting so don't add the berries if you're not ready to serve the cake yet
Chill in the fridge for 1 hour to firm up the frosting before serving
Store any leftovers in the fridge and eat within 3 days