1. Heat oven to 350°F. Grease 13x9x2-inch baking pan.
2. Stir together cookie mix, 1/2 cup pecans and butter; mix until crumbly. Press 2-1/2 cups crumb mixture onto bottom of prepared pan. Bake 10 minutes.
3. Meanwhile, add remaining pecan pieces and 1/3 cup toffee bits to remaining crumb mixture. Set aside. Stir together sweetened condensed milk, egg, flour and vanilla in medium bowl. Stir in remaining toffee bits.
4. Pour sweetened condensed milk mixture over partially baked crust. Top with remaining crumb mixture; press down lightly.
5. Bake 25 to 30 minutes or until edges are brown and bubbly and center is set. Cool completely in pan on wire rack. About 36 bars.