Preheat oven to 350F.

In a bowl, cream together butter and brown sugar in either a stand mixer or with a hand mixer.

Add in the egg, vanilla.

Mix until combined.

Add the bourbon and mix well to combine.

Add in the peanut butter and mix until combined.

Add in the flour and mix just until combined.

Break the pretzels into large pieces.

Fold in the pretzels gently as not to break up the pretzel pieces too much.

Spread the batter in an 8x8 baking pan sprayed with non-stick spray.

Spread pretzel pieces or whole pretzels on the top of the batter and press in slightly to get the pretzels to stick.

Bake at 350F for 20 minutes or until the middle is set and a toothpick comes out nearly clean.  A few crumbs are ok.

Cool completely.

Cut and store in an airtight container for up to a week.