Preheat oven to 350°F. Spray a 9×13 pan lightly with cooking spray.
Beat butter and sugars until light and fluffy. Add eggs and vanilla, mix until incorporated.
On low speed add in salt, baking soda, malted milk powder, and flour a little at a time, mixing until just incorporated.
Using a wooden spoon or spatula, stir in approx. 1 cup of the chocolate chips and pretzel pieces by hand, as not to break up the pieces too small.
Spread in prepared pan and bake for 25 minutes. Let cool completely.
When cooled pour peanut butter caramel over the bars and spread evenly. Chill in fridge for 15 minutes to set caramel.
On the stovetop or in a microwave safe measuring cup, heat ¼ cup cream until steaming, and while hot, pour over approx. 1 cup chocolate chips in a small bowl. Whisk until smooth and chocolate is completely melted. Carefully spread chocolate over set caramel. While still wet, add pretzels for garnish if desired.
Put back in the fridge for at least 30 minutes or until chocolate is set. Cut into squares when ready to serve.