1. Prepare an ice-water bath; set aside. Add 1/2 cup water and the apple juice to a medium bowl; sprinkle with gelatin. Let soften about 5 minutes. Combine wine and sugar in a small saucepan; bring to a boil over high heat, stirring occasionally to dissolve sugar. Reserve 8 blackberries for garnish; add remaining blackberries to the saucepan. Reduce heat, and simmer 5 minutes. Slowly stir hot wine mixture into gelatin mixture. Transfer bowl to ice-water bath, and stir gently until cool, about 5 minutes.

2. Pour mixture into a 9-by-5-by-2 1/2-inch nonreactive metal loaf pan. Refrigerate, covered, until set, about 45 minutes, or up to overnight. To unmold, set pan in warm water until gelatin loosens, about 2 seconds; invert onto a cutting board. Use a knife to break seal along edges if necessary. Cut gelatin into 1 1/2-inch cubes. Divide among 4 small bowls. Garnish each with 2 blackberries and mint leaves.