Line a square 9x9 baking dish with parchment paper.
Add the butter and peanut butter to the bowl of a stand mixer fitted with the paddle attachment and beat on medium speed until well combined. Scrape down the sides of the bowl as needed.
With the mixer on low speed, add the vanilla extract and then slowly add the powdered sugar.
Once all of the powdered sugar has been added, allow the mixer to run on low speed until it all comes together in a ball.
Transfer the peanut butter to the parchment lined pan and pack it down, making sure to press it all the way to the edges.
Add the chocolate chips and coconut oil to a small, microwave safe bowl and microwave until melted.
Pour the chocolate mixture over the peanut butter layer and use a spoon or offset spatula to push the chocolate into an even layer.
Transfer the bars to the refrigerator and allow them to sit until the chocolate has fullly hardened - about 2 hours.
Slice the bars and top with flakey sea salt, if desired.
Notes
SUBSTITUTIONS
Chocolate Chips: Dark or semi-sweet chocolate works best, but you can use whatever you have on hand.
STORAGEStore in an airtight container in the fridge for up to 3 days.