Preheat oven to 400 F.
Place the pumpkin on a rimmed baking sheet and roast until tender (30-60 minutes, depending on how large it is). When cool enough to handle, scoop out the pumpkin flesh and place in the bowl of a food processor. Pulse until smooth. Measure out 1 1/2 cups, and set the rest aside for a later use. Reduce oven temperature to 350 F.
In a large bowl, sift together both spelt flours, cinnamon, cardamom, nutmeg, cloves, ginger, baking powder, baking soda, salt, and chia seeds. Set aside.
Return the 1 1/2 cups of pumpkin puree to the food processor. Add the date syrup, olive oil, and banana. Blend to combine. Add the wet ingredients to the bowl of dry ingredients and stir to combine. Quickly whisk in the apple cider vinegar.
Pour the batter into 2 8-inch springform cake pans. Bake for 30 minutes, or until a toothpick inserted into the center comes out clean.
Scoop out the solid, creamy top layer from the chilled cans of coconut milk, leaving the watery liquid for another use. Place the coconut cream in a large bowl and add the creamed honey. Whisk together. Fold the vanilla seeds into the coconut cream and honey mixture. Place bowl in refrigerator.
When the cake has cooled, remove from pans. Use a large, serrated knife to slice off the mounded top of the cakes. Slice both cakes in half to create 4 layers. Place layers on wire racks to cool completely.
When 100% cool, place one of the cake layers on a cake stand or plate. Top with about 1/4 of the icing, and spread into an even layer. Sprinkle with some of the chopped hazelnuts. Repeat with the remaining cake layers, icing, and hazelnuts, topping the cake with a final layer of icing and sprinkling of hazelnuts. Serve and enjoy!