Melt the Butter: In a medium microwave-safe bowl, melt the unsalted butter in the microwave (about 30-40 seconds). Allow it to cool slightly.
Mix Wet Ingredients: Add the granulated sugar to the melted butter, mixing well with a whisk or spatula until combined. Add the eggs, one at a time, whisking well after each addition. Stir in the vanilla extract until fully incorporated.
Combine Dry Ingredients: In a separate bowl, sift together the all-purpose flour, unsweetened cocoa powder, salt, and baking powder.
Blend the Mixtures: Gradually add the dry ingredients to the wet mixture, stirring until just combined. Do not overmix. Fold in the semi-sweet chocolate chips and walnuts (if using).
Prepare Air Fryer: Preheat the air fryer to 320°F (160°C) for about 5 minutes. While it’s preheating, line a 6-inch round baking pan or an air fryer-safe baking dish with parchment paper.
Pour Batter into Pan: Pour the brownie batter into the prepared baking pan, spreading it evenly.
Air Fry the Brownies: Carefully place the baking pan in the air fryer basket. Cook at 320°F (160°C) for 15-18 minutes. Check for doneness by inserting a toothpick into the center; it should come out slightly damp but not wet.
Cooling: Once cooked, remove the pan from the air fryer and let the brownies cool in the pan for 10 minutes. Then, lift them out using the parchment paper and allow them to cool completely on a wire rack.
Serve: Once cooled, cut into squares and enjoy your decadent double chocolate brownies with a scoop of ice cream or a drizzle of chocolate sauce if desired!
Notes
Optional walnuts can be included for added texture.