4 ounces fresh mozzarella cheese, cut into 6 slices
10 fresh basil leaves, divided
3/4 cup balsamic vinegar
1 tablespoon granulated sugar
1/2 teaspoon crushed red pepper flakes
1 teaspoon salt
Preheat oven to 350°F. Spread walnuts in one layer on ungreased shallow baking pan. Bake for 10-15 minutes, stirring occasionally, until golden. Set aside.
In food processor bowl place 1 cup walnuts; pulse until chopped. Add butter and garlic to walnuts; process until finely chopped.
Evenly divide walnut mixture and firmly press into bottoms of 6-cup muffin pan (approximately 2 tablespoons per cup).
Bake 5 to 6 minutes, or until lightly browned.
Layer one tomato slice over baked crust, add mozzarella slice, basil leaf and top with tomato slice. Repeat until all 6 cups are filled.
Bake 8 to 10 minutes or until cheese has melted. Remove from oven; allow to rest 5 minutes before removing from pan.
Meanwhile, in a saucepan over medium heat, combine balsamic vinegar, sugar, red pepper flakes and salt; cook while stirring occasionally until reduced by half.
Coarsely chop remaining ½ cup walnuts.
To serve caprese cups, drizzle small amount of balsamic reduction sauce on appetizer plate. Place caprese cup over sauce; top with remaining basil that has been finely chopped and the toasted walnuts. Serve immediately.