1. At least 2 weeks before you plan to bake the cakes, place prunes, raisins, currants, cherries, citrus peel, candied ginger, rum, and port in a large container with a lid. Stir fruit once a day.

2. When ready to bake the cakes, preheat oven to 250 degrees. Butter and flour two 9-by-5-by-3-inch loaf pans and two 8-by-2-inch round cake pans and line with parchment; butter parchment and set aside.

3. In the bowl of a food processor or the jar of a heavy-duty blender, grind almonds to a coarse meal. Stir ground almonds into the fruit mixture until well combined. Working in batches, transfer almond-fruit mixture to the bowl of a food processor or jar of a blender and pulse until a chunky paste forms. Transfer paste to a large bowl or a rimmed baking sheet.

4. In a small bowl, whisk together boiling water and cocoa powder until smooth; set aside.

5. In the bowl of an electric mixer, cream together butter and brown sugar. Scrape down the sides of the bowl, add vanilla, and beat in eggs, one at a time. Transfer to a very large bowl or stock pot.

6. In a large bowl, whisk together flour, baking powder, cinnamon, nutmeg, and baking soda. Using a spatula, fold flour mixture into butter mixture. Add cocoa powder mixture and molasses and fold to combine; stir in fruit.

7. Divide batter evenly between prepared pans and bake until cakes are firm on top and a cake tester inserted into the center comes out clean, about 3 hours. Remove from oven and immediately brush tops of cakes with rum. Let cakes cool completely.

8. Invert cooled cakes to unmold and brush with additional rum. Wrap cakes in cheesecloth, a clean dish towel, or sturdy paper towels, and then in aluminum foil. Let stand at room temperature at least 3 days before serving, and up to 1 month. Serve cakes dusted with confectioners' sugar or frosted with royal icing.