Step 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.

Step 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.

Step 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.

Step 4

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

Step 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.

Step 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.

Step 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.

Step 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.