Line a square baking pan with parchment paper, leaving a bit of an overhang to so the finished bars can easily be removed. I like 8x8. 9x9 works nicely too.
Melt butter and brown sugar and vanilla in large sauce pan. Stir and cook over medium heat until creamy and smooth. Sugar should be disolved
Stir oats into the butter mixture and continue to stir and mix over medium heat until the oats are evenly coated. About 3 minutes. The mixtue might bubble a little and that is okay.
Cover the bottom of the sqaure baking dish with about half of the oat mixture. Pressing the mxiture firmly to make a crust. I use the bottom of a measuring cup to flatten and smooth out the oats to make an even layer.
In a microwave safe bowl, heat chocolate chips and peanut butter together until the chocolate chips melt and the mixture smooth and creamy. Do this in 30 second increments, stiring after each. It should only take a minute or two. Once the chocolate starts to melt, it will blend smoothly. Pour over the oatmeal crust and spreading almost to the corners.
Top with the remaining oatmeal mixture, gentily pressing into the chocolate. It's okay if you see some chocolate.
Refrigerate for several hours, or overnight until chocolate is firm. Remove from plan and cut into squares.
To keep these treats gluten-free, choose certified gluten-free oatmeal.To keep these treats vegan, make sure your chocolate is dairy-free.These bars need about 3 hours in the fridge to fully harden. So plan ahead.