Preheat the oven to 170c. Grease and line two 7 inch cake tins with baking paper
Place the butter in a large bowl (or bowl of a stand mixer with paddle attachment) along with the sugars, then cream together until light and fluffy. Add the eggs one at a time, beating well between each addition- you can add a heaped spoonful of the flour at this stage too if you’re worried about the mixture curdling. Once the eggs are incorporated fold in the remaining flour, bicarbonate of soda, salt, baking powder and spices. Stir through the pumpkin, sultanas and pecans.
Split the batter between the cake tins and bake for 30-40 minutes or until a skewer comes out clean or with just a few moist crumbs attached when inserted. Leave the cakes to cool completely in the tins
While the cakes are cooling make the icing by simply whisking the mascarpone, double cream and icing sugar together until pipe-able.
To assemble, slice the two cakes horizontally, leaving you with 4 even layers. If you’d like to pipe your icing, pile it into a large piping bag and snip a 1cm hole in the end. Pipe little peaks all over the surface of the first layer, then add the next and repeat the process until you’ve used up all of the cake layers and icing. If you don’t want to pipe just spread the icing in an even layer between the layers. Decorate the top with pumpkin seeds and chopped pecans- or add fun toppers if you like!