Heat oven to 350°F. Spray 13x9-inch pan with cooking spray. In large bowl, mix granulated sugar, butter, 1 teaspoon vanilla and 1 egg. Stir in flour. Press dough in bottom and 1/2 inch up sides of pan (if necessary, use floured fingers).
Bake 10 to 15 minutes or until edges are light brown.
Meanwhile, in medium bowl, beat filling ingredients except pecans with spoon. Stir in pecans. Pour over crust.
Bake 25 to 30 minutes or until set. While warm, loosen edges from sides of pan. cool completely, about 2 hours.
For triangular bars, cut into 6 rows by 3 rows. Cut each bar in half diagonally. In small microwavable bowl, microwave chocolate chips and shortening uncovered on High 1 minute to 1 minute 30 seconds or until melted; stir until smooth. Dip 1 side of each bar into melted chocolate; lay flat to dry.