Heat oven 350F. Lightly coat a 9-by-13-inch baking dish with no-stick cooking spray and line with parchment paper leaving a small overhang. 

In a medium bowl, whisk together the flour, baking powder, and 1 ½ teaspoons of salt; set aside.

In the bowl of an electric mixer, beat 1 cup of butter, peanut butter, sugar and brown sugar until light and fluffy. Add the eggs, 1 at a time, followed by 2 tablespoons of bourbon.

Stir in the flour mixture just until combined.

Gently press about ⅔ of the dough into an even layer over the bottom of the prepared baking dish.

In a microwave safe dish, heat the condensed milk, bittersweet chocolate, 2 tablespoons of butter and ¼ teaspoon of salt, stirring every 30 seconds until chocolate is melted and mixture is smooth. Stir in remaining 2 tablespoons of bourbon.

Spread chocolate mixture evenly over dough in pan.

Crumble or dollop the remaining dough on top.

Sprinkle the top with semisweet chocolate and peanuts; gently press down.

Bake for 45 to 50 minutes, or until golden on top.

Cool completely in the pan before cutting into bars.