Combine butter and chocolate in a microwave safe stirring every minute. Stir; cool 10 minutes. Mix together egg, brown sugar, vanilla and salt in a small bowl. Stir into chocolate mixture. Add flour; mix well. Spread batter in an 8"x8" baking pan lined with aluminum foil and sprayed with nonstick vegetable spray. Bake at 350 degrees for 15 minutes or until a toothpick inserted near center comes out clean. Cool completely on a wire rack. Cover; chill until firm. Cut brownies into8 squares. Spread 4 brownies with ice cream; top with remaining brownies. Wrap in plastic wrap; freeze overnight. To serve, drizzle with warm chocolate sauce.