1-First, preheat your oven to 350°F (175°C) and line an 8-inch square baking pan with foil, then spray it with non-stick cooking spray. This step makes cleanup a breeze and ensures your blondies come out perfectly. In a medium bowl, whisk together the flour, baking soda, baking powder, cornstarch, and salt to combine the dry ingredients evenly.

2-Next, in a large bowl, combine the melted butter and sugar until well mixed. Add the egg and yolk, mixing until incorporated, then whisk in 4 ounces of cookie butter for that creamy flavor. For more tips on getting the texture just right, check out our advanced tips section to avoid common mistakes.

3-Now, fold in the dry ingredients and chocolate chips gently to keep the batter light. Pour half the batter into the prepared pan, swirl in the remaining 2 ounces of cookie butter for an extra burst of flavor, then add the rest of the batter on top. Sprinkle with sea salt and bake for 24 to 29 minutes until set and golden brown. Let it cool for at least 30 minutes before slicing, and remember, the recipe yields between 9 and 16 bars in about 35 minutes total, with 10 minutes prep and 25 minutes baking.