Stir together the maple syrup and peanut butter in another medium bowl until smooth. Add the salt, vanilla, powdered peanut butter, and oat flour and mix until combined then add the powdered sugar a little at a time and mix to incorporate into a thick dough.
Scrape the filling mixture out onto the base cookie dough layer and also press it down to form an even peanut butter layer on top of the chocolate dough.
Now scrape out the remaining chocolate dough over the filling layer and crumble evenly over it for the top layer.
Bake the bars for 18 to 22 minutes until the top is starting to darken and brown on the edges. Remove from oven and, if desired, immediately sprinkle some additional chopped pb cups over top and press down very gently. Allow the bars to cool completely before cutting.
Click the link above for the drizzle to finish the bars.