In a small saucepan or microwave safe bowl, cover the prunes with water and bring to a boil or microwave on High for 2 minutes. Remove from heat and allow to rest, covered, for about 1 hour. Drain thoroughly and chop or mash.
Preheat the oven to 350° F/175° C.
In the mixing bowl, cream together the sugar and butter until light and fluffy. Add the eggs and beat until creamy. Add the cooked prunes and mix on low just until they are distributed.
In the medium bowl, sift together the flour, baking powder, salt, cinnamon, cloves, and allspice. Stir the milk and baking soda together in the measuring cup. Add 1/3 of the flour and half the milk mixture to the butter and eggs, and mix well. Repeat, then add the remaining flour, mixing thoroughly. Stir in the raisins and chopped nuts.
Bake in the preheated oven until a test toothpick comes out clean, about 1 hour. Remove from the oven and allow to cool in the pan for 10 minutes, then turn out onto a wire rack and allow to cool completely. Wrap tightly with plastic wrap to keep it fresh. Will keep in the freezer wrapped tightly and stored in a freezer bag for up to 3 months.
Due to the density and moisture content, the cake will keep on the counter for a few days as long as you wrap it tightly in plastic wrap. After than you may want to freeze any remaining, but unlike fluffy cakes this one loves the freezer and thaws beautifully.