Step 1

Preheat oven to 350°F. Coat a 13- x 9-inch baking dish with cooking spray. Stir together flour, pecans, and butter in a bowl. Press mixture into prepared baking dish in a thin layer, patting mixture evenly into all corners. Bake until set, about 20 minutes. Remove from oven; cool about 30 minutes.

Step 2

Beat cream cheese with an electric mixer on medium speed until creamy, about 2 minutes. Gradually add powdered sugar, beating until well blended, 45 seconds to 1 minute. Fold in 1 cup of the thawed whipped topping. Spread mixture evenly over cooled crust.

Step 3

Whisk together milk and the chocolate and vanilla pudding mixes in a large bowl until well combined. Let stand until slightly set, about 10 minutes. Pour mixture over cream cheese layer; spread with remaining whipped topping. Drizzle with chocolate syrup if desired. Cover, and chill at least 2 hours or up to 8 hours.