1Heat oven to 350°F. Spray bottom of 15x10x1-inch pan with cooking spray. In large bowl, stir brownie mix, water, oil and eggs until well blended. Stir in 1/2 cup pecans; spread in pan.
2Bake 15 to 17 minutes or until center is set. DO NOT OVERBAKE. Cool completely on wire rack, about 45 minutes.
3Spoon ice cream evenly over brownies; smooth with back of spoon or rubber spatula. Freeze uncovered until firm, about 3 hours.
4To serve, drizzle hot fudge topping over dessert with fork using quick strokes. Sprinkle with 1/2 cup pecans. Let stand at room temperature about 5 minutes before cutting. Serve topped with whipped topping.