In a large enough microwavable bowl melt 1 stick of butter. Add peanut butter and stir to mix well. When the mixture is cool enough break 2 eggs in and mix well. Then add cake mix and with a wooden spoon mix until everything is incorporated. Add the whole bag of peanut butter chips a little at a time and mix well.
Spray an 8x10 cake pan and press the cake mixture into the bottom. Reserve 1 1/2 cup of the mixture
In another microwavable bowl melt the 2 tablespoons of butter. Add the can of sweetened condensed milk and the bag of chocolate chips. Microwave for 1 minute and stir and repeat. In my microwave it only took 2 minutes for the chocolate to melt. When you take it out stir and then add in 2 teaspoons of vanilla extract. Work quickly so the mixture doesnt get cold and start to get stiff. Spread the melted chocolate over the cake mixture.
Take the reserved cake mixture and evenly sprinkle it over the top.
Bake for 25-30 minutes. Allow it to cool completely for a few hours or overnight so it sets before you cut the bars.