01 -
Line an 8-inch square pan with parchment paper, leaving overhang on two sides for easy lifting.
02 -
Combine chocolate chips and peanut butter in a small saucepan over low heat. Stir until smooth and glossy, then reserve 2 tablespoons for drizzling.
03 -
Melt butter in a large saucepan over medium-low heat. Stir in brown sugar and salt until combined, then add vanilla and oats. Cook on low for 2 minutes, stirring constantly.
04 -
Transfer half of the warm oat mixture to the prepared pan. Press firmly into an even layer with a greased spatula or the bottom of a measuring cup.
05 -
Spread the chocolate peanut butter mixture over the oat base in an even layer.
06 -
Crumble the remaining oat mixture over the chocolate and press lightly. Drizzle with the reserved chocolate and sprinkle with flaky salt if using. Chill for at least 2 hours, then rest 10 minutes before slicing.