Combine dried fruits in food processor and pulse until finely chopped. Transfer to a large bowl and add nuts, dark rum, vanilla and almond essence and 60g brown sugar. Cover and soak in the rum overnight then transfer to a saucepan. Add 250ml cold water and heat over high heat until begins to simmer then reduce to low heat and cook 15 minutes or until fruits soften. Allow to cool.
Sift flour with allspice, nutmeg, cloves, baking powder and ½ teaspoon salt in a bowl and set aside.
Use an electric mixer to cream the butter and the remaining brown sugar until pale and fluffy. Add eggs, one at a time, beating well after each addition. Add fruit mixture and stir well to combine, then add reserved flour mixture and combine well.
Preheat the oven to 150°C/300°F/gas 2. Grease a 28cm-diameter springform cake tin with a little softened butter, then sprinkle a little flour around the sides and bottom and shake out excess flour. Spoon cake mixture into cake tin and bake for 2 hours or until a skewer poked in the middle of the cake withdraws clean from the cake. Remove cake from the oven and prick all over with the skewer. Combine port and rum in a jug and pour over the cake. Allow to stand for 3 hours before removing from the springform cake tin.
For the icing, combine sugar, golden rum, cream of tartar, ¼ teaspoon salt and 180ml cold water in a saucepan and cook over low heat until mixture reaches 118C (soft ball stage) on a sugar thermometer. Meanwhile, beat egg whites in a mixer to soft peaks then gradually add hot syrup and vanilla to egg whites, beating constantly for 10 minutes or until icing cools and is of spreadable consistency.
Ice cake immediately with a palette knife and serve with garnish of cedro and clementines on top.