Try This

Step One: Find your favorite brownie mix or brownie recipe.
Step Two: Make the batter. Lick your finger unless raw egg worries you. Maybe I should worry more, but I always have a little taste.
Step Three: Pour batter into your pan.
Step Four: Get out a big spoon, like a soup spoon. Using that, scoop dabs of peanut butter straight from the jar on top of the batter. Repeat until you have equally blessed all parts of the batter. With a butter knife, swirl it around a little bit (not too much) to distribute.
Step Five: Grab some pretzels. Crush 'em up a little bit. You still want bigger pieces, though.
Step Six: Bake according to your recipe.

Note: Take to heart the life experience of a friend who just followed the above steps. Do not eat brownies for dinner and breakfast right before a glucose test at the Doctor. This may or may not cause some wacky readings. I maintain this is not my fault but was told I may or may not be getting a phone call.