This makes a nice little batch of slow cooker peanut butter chocolate chip blondies in a 2 to 3-1/2 quart slow cooker. You can double the batch for a 4-Quart slow cooker or triple for a 6-Quart. But if you're a Weight Watcher, I wouldn't suggest it unless you have someone to share them with!!
Generously grease the inside of your slow cooker with butter. Then add a little flour and tilt it all around to coat the sides and bottom. Dump out any excess flour. (Or coat the bottoms and sides with non-stick spray with flour, which is what I did.)
In a bowl, whisk together the flour and baking powder and then set it aside.
With an electric mixer at medium speed beat together the butter, peanut butter, sugar and brown sugar until light and creamy. Beat in the egg until it is fully incorporated. Beat in the vanilla until the mixture is smooth.
Scrape down the sides of the bowl with a rubber spatula and remove the beaters. Add the flour mixture and gently fold it in with the spatula until it's just blended. Gently stir in the chocolate chips.
Scrape and smooth the batter into the prepared slow cooker. (It will be thick.)
Place several layers of paper towels on top of the slow cooker and then set the lid in place.
(This will prevent condensation from dripping back into your blondies while they bake.) Cook on HIGH about 1-1/2 hours. Or until the blondies are firm throughout and a little bit dry at the edges and set to the touch in the middle. Remove the insert from the cooker and set it on a wire rack for 30 minutes to cool.
If desired, invert the insert on a cutting board, shake gently to release the blondies ,then remove the insert and turn the blondies right side up.