Prepare and preheat
Preheat oven to 350°F (175°C). Grease the 8×8 inch baking dish with butter and line it with parchment paper.

Make the batter
In a mixing bowl, mash the bananas with a fork until smooth. Add the egg and monkfruit sweetener, then mix until combined. Add the ground oats, cocoa powder, baking powder, baking soda, vanilla extract, and a pinch of salt. Stir thoroughly until all ingredients are well incorporated and the batter is uniform.

Add chocolate
Fold in the chocolate chips or sprinkle them evenly on top of the batter when spread in the baking dish.

Prepare peanut butter swirl
In a small bowl, combine the PB2 powdered peanut butter with enough sugar free syrup to create a thick, spreadable sauce. Swirl the peanut butter mixture over the top of the brownie batter.

Bake and cool
Bake in the preheated oven for 20 minutes. Remove from the oven and allow to cool slightly before slicing and serving.