Line an 8-inch-by-8-inch baking dish with parchment paper, and set aside.
In a medium saucepan, combine the butter, brown sugar and vanilla extract. Heat over low heat, until the butter has melted and the sugar has dissolved.
Add the oats, cinnamon, and kosher salt. Cook, stirring constantly, for 4 to 5 minutes.
Pour half of the oat mixture into the prepared baking dish. Spread out the mixture evenly, pressing down.
In a small microwave-safe bowl, combine the chocolate chips and the peanut butter. Heat on high in the microwave, in increments of 40 seconds, stirring in between each increment, until melted and fully combined.
Pour ⅘ of the chocolate mixture into the pan over the pressed oats, reserving about ¼ cup for drizzling. Top with the remaining oats and drizzle with the remaining ¼ cup chocolate mixture.