Lightly coat a 5-quart slow-cooker insert with non-stock olive oil cooking spray.In a small bowl, stir peanut better, sugar, and butter until combined.
Stir in 2 eggs and vanilla. Optional: Sprinke in some ground flax seed.Add flour and baking powder.
Toss in chocolate chips to your liking (about ¾ cup).Add batter to slow cooker.
Evenly spread.Cover and cook on low, 3 1/2 hours.
Uncover and cook 30 minutes.Remove insert from slow cooker and run a knife around edge to loosen brownies.Let cool completely on a wire rack, about 2 hours.