Add the butter, flour and powdered sugar into a mixing bowl. Mix on medium speed until well blended and the mixture comes together. Press evenly into a 9 x 13 inch cake pan. Bake at 350 degrees for 20 minutes. While the base is baking, add the sweetened condenced milk and 2 tbsp butter into a small saucepan. Stir constantly over medium heat for 5-10 minutes or until butter is melted and the mixture just starting to simmer. Remove from heat. When the base layer is baked remove from oven and spread the milk mixture over top. Bake this in the oven for 12 minutes. Remove from oven and sprinkle the chocolate chips evenly over the top. Bake for 2 minutes, the chips should be shiny and soft. Spread evenly. Top with the heath bits. Cool completely. Store at room temperature in a covered container for up to 1 week. Can also be frozen to be enjoyed at a later date.
