Pecan Toffee Squares

1 (14 ounce) can sweetened condensed milk

1 egg, beaten

1 cup chopped pecans

1 (8 ounce) package toffee baking bits

1 teaspoon vanilla extract

½ cup butter, softened

1 (18 ounce) package yellow cake mix

1 egg, beaten

1 (8 ounce) container frozen whipped topping (such as Cool Whip®), thawed

Preheat an oven to 350 degrees F (175 degrees C). Grease a 9x13-inch baking pan. Mix sweetened condensed milk, 1 egg, pecans, toffee bits, and vanilla extract in a bowl until well blended; set aside.

Cut the butter and 1 egg into the yellow cake mix in a large bowl with a knife or pastry blender until the mixture resembles coarse crumbs. Press the crumbs into the prepared pan to form a bottom layer.

Bake in the preheated oven until firm, about 7 minutes. Spread pecan filling over the baked bottom layer, then continue baking until the filling has set, 22 to 30 minutes. Cool completely on a wire rack. Serve with whipped topping.