Preheat the oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper and lightly grease the sides.
Mix the wet ingredients:In a large bowl, stir together the melted butter, peanut butter, brown sugar, and honey until smooth. Add the egg and vanilla and whisk until fully combined.
Add the dry ingredients:Stir in the oats, oat flour, cinnamon, baking soda, and salt until a thick batter forms. Fold in the chocolate chips.
Bake: Spread the batter evenly into the prepared pan and smooth the top. Sprinkle with extra chocolate chips if desired. Bake for 22–25 minutes, or until the edges are golden and the center looks set. Cool & slice:Let cool completely in the pan before slicing into bars. For clean slices, chill in the fridge for 10–15 minutes before cutting.
