1. Preheat oven to 350°
2. In a medium bowl, combine cracker crumbs and brown sugar. Stir in butter. Press mixture firmly into bottom and up sides of a 10-inch springform pan. Bake for 8 minutes; let cool completely. Gently spread softened Key Lime Ice Cream over crust. Cover and freeze for 4 hours, or until firm. Cut into wedges to serve. Garnish with fresh lime slices, if desired.
Key Lime Ice Cream
1. In a large bowl, beat cream at medium speed with an electric mixer until slightly thickened. Gradually add sugar, beating until soft peaks form. Add condensed milk and beat until stiff peaks form. Beat in lime juice, lime zest, and half and half.
2. Pour mixture into freezer container of a 1-gallon electric ice cream maker, and freeze according to manufacturer's instructions. If a firmer texture is desired, transfer ice cream to an air-tight container, and freeze for 2 hours, or until firm.