In a small bowl, combine all the ingredients except the gelatin with 3 tablespoons water, cover, and refrigerate for 48 hours. Strain. Soak the gelatin sheets in a bowl of ice water for 10 minutes; squeeze dry. In a small saucepan, heat one-quarter of the strained liquid to just below a simmer. Remove from the heat, stir in the gelatin to dissolve, add the remaining liquid, and strain into a flat, rimmed container to reach ¼-inch thickness. Refrigerate, flat, for 4 hours, or until firm. Cut into ¼-inch cubes. Reserve, chilled.