Preheat oven to 350 degrees F. Coat 9-inch pie plate with nonstick cooking spray. Combine crackers and walnuts in small bowl. Dust plate with 2 tablespoons cracker mixture.
Beat egg whites in bowl with electric mixer until foamy. Add salt; beat until soft peaks form. Beat in sugar, 2 tablespoons at a time, until stiff peaks form. Gently fold in remaining cracker mixture until just blended. Spoon meringue into pie plate; form crust by spreading meringue from center to edges to cover plate completely.
Bake in preheated 350 degree F oven for 20 to 25 minutes or until meringue is golden brown. Transfer to wire rack to cool completely.
Spoon softened ice cream into cooled meringue crust. Cover with plastic wrap and freeze 3 hours or until ice cream is firm.
Meanwhile, combine blueberries, raspberries, strawberries and melted jelly in a large bowl; gently toss to coat completely.
To serve, spoon the berry mixture over the top of the pie, mounding berries in the center. Drizzle with the melted chocolate. Garnish with mint if you wish.