Clean the raisins and chop up all the dry fruits into small bits. Transfer them into a bowl and add the orange juice and mixed spice. Give everything a good mix. Either cover the bowl with cling film or transfer the fruits into a glass or ceramic jar and fasten the lid. Keep aside for 6-8 hours or overnight.
When you are ready to bake, start by greasing an 8" round baking tin with butter and line it with baking parchment. Keep aside.
Preheat oven to 120 C for 15 minutes.
Add about 1 teaspoon of flour into the chopped nuts to keep them from sinking to the bottom of the cake.
In a bowl, add the butter and sugar and beat until pale and fluffy. Now add one egg at a time beating well after each addition.
Add the orange and lemon zest, stir in the treacle/black caramel and mix well.
Sift in the flour, baking powder, salt & mixed spice.
Add the soaked fruits and its liquid. Stir in the nuts rolled in flour. Fold everything together
Spoon the batter into the prepared tin and bake in the preheated oven for 2-1/2 to 3 hours or till the skewer inserted comes out clean. *See notes
Once done, remove and place the tin on a cooling rack for 20 minutes before unmolding the cake. Leave it uncovered till completely cooled.
You can now decorate it as desired with marzipan or just keep it plain. Cut, serve & enjoy.