Start by placing your unsalted butter in a saucepan over medium heat. Allow it to melt and then continue to cook, swirling the pan occasionally until the butter turns a beautiful golden brown and develops a nutty aroma. This should take about 5-7 minutes. Be careful not to burn it!
Once your butter is browned, remove it from heat and let it cool slightly. In a large mixing bowl, whisk together the brown sugar and the brown butter until well combined. Add in the egg and mix until smooth.
In a separate bowl, whisk together the flour, baking powder, and cinnamon. Gradually add this dry mixture to the wet ingredients, stirring until just combined. Be careful not to overmix!
Fold in the semi-sweet chocolate chips (or chunks!) and toasted walnuts using a spatula, ensuring they’re evenly distributed throughout the batter.
Preheat your oven to 350°F (175°C). Line your baking pan with parchment paper if using, and pour the batter into the prepared pan. Spread it evenly and sprinkle the top with flaky sea salt. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Allow the blondies to cool in the pan for at least 10 minutes before transferring them to a wire rack to cool completely. Once cooled, slice them into squares and enjoy!
