Preheat oven to 350°. Line a muffin tin with 12 paper cupcake liners. Combine first 6 ingredients in a food processor; process until nuts are ground and mixture is thoroughly blended. Press into bottoms and partially up sides of prepared cups. Bake 5 minutes; cool completely.
Stir together ice cream, lime zest, and lime juice in a mixing bowl. Spoon about 1/4 cup ice cream mixture into each crust; freeze until firm. Garnish, if desired.