Preheat oven to 400°F (200°C).

Line a 13x9-inch pan with foil, extending the ends over the sides; spray with cooking spray.

Combine flour, chopped toasted pecans, sugar, melted butter, and 1/2 cup of toffee bits in a bowl.

Press the mixture evenly onto the bottom of the prepared pan to form the crust.

Bake for 10 minutes, or until the crust is lightly browned.

Remove from the oven and let cool completely.

In a separate bowl, beat the butterscotch pudding mixes and cold milk with a whisk for 2 minutes until well combined.

Spread 1 1/2 cups of the butterscotch pudding evenly over the cooled crust.

Add half of the Cool Whip whipped topping to the remaining pudding mixture.

Whisk until blended and smooth.

Spread the pudding and Cool Whip mixture over the pudding layer in the pan.

Top with the remaining Cool Whip.

Sprinkle the remaining toffee bits over the top.

Refrigerate for at least 3 hours, or until firm, before serving.

Lift the dessert from the pan using the foil overhang and cut into bars to serve.