14ounce(½ can) sweetened and condensed milk (about ½ cup)
Preheat the oven to 350 degrees Fahrenheit and spray a 9x13 inch pan with cooking spray or grease it with butter.
To make the cookie layer, beat the salted butter, brown sugar, and granulated white sugar together in a large bowl with a stand or hand mixer until creamy.
Add in the eggs and peanut butter. Beat until combined.
In a separate medium sized bowl, whisk together the all-purpose flour and baking powder.
Add the flour mixture to the wet ingredients and beat until just combined.
Fold in the pretzels and semi-sweet chocolate chips.
Pour the batter into the baking pan and spread it out evenly.
Bake in the oven for 35-40 minutes or until the middle starts to brown and set.
Remove from the oven and let cool for 20-30 minutes.
When there are 5-10 minutes left of cooling time, prepare the optional chocolate layer.
Melt the rest of the chocolate chips and the sweetened and condensed milk in a skillet over medium heat for about 5 minutes, stirring frequently to keep from burning. The chocolate chips should melt and combine completely with the sweetened and condensed milk, and the mixture will thicken slightly once it has cooled, which only happens with those few extra minutes of stirring.
Once melted, pour the chocolate glaze over the completely cooled cookie in the baking pan. Be sure the chocolate layer covers the entire pan.
Lay pretzels down evenly on top of the chocolate layer.
Let chill in the refrigerator until the chocolate layer sets, about 20-30 minutes.
Cut into bars and serve cold.
To Store: Store these bars in an airtight container. They will stay fresh for 2 days if kept at room temperature or put them in the refrigerator for up to 6 days
To Freeze: Freeze your bars in a freezer-safe container for 3-4 months.
When spreading the chocolate glaze over the top, you can tip the baking dish back and forth and use gravity to cover the whole dessert evenly.
While these bars are pretty easy to cut and get out of the dish, to make it even easier you can line the dish with parchment paper instead of cooking spray. That way, you can lift the entire dessert out of the dish all at once.