1Line 24 mini muffin cups with petit four paper cups. Cut 2 (1 1/4-inch) rounds from each cake slice. Place 1 cake round in bottom of each cup.
2In small bowl, mix water, coffee granules and 1/2 teaspoon of the rum extract. Drizzle about 1/2 teaspoon of the coffee mixture over cake in each muffin cup. Set aside.
3In medium bowl, beat cheese, powdered sugar and remaining 1 teaspoon rum extract with electric mixer on medium speed until creamy. In another medium bowl, beat whipping cream on high speed until soft peaks form. On low speed, beat cheese mixture into whipped cream. Spoon or pipe a rounded tablespoon whipped cream mixture into each cup, covering cake.
4Grate semisweet chocolate over each cup. Top each with coffee bean. Refrigerate at least 4 hours to blend flavors. Store covered in refrigerator.