Prepare the Baking Pan: Start by preheating your oven to 350°F. Line an 8x8 inch baking pan with parchment paper or lightly grease it so the brownies lift out easily later.
Mix the Wet Ingredients: In a large mixing bowl, whisk together the melted butter, granulated sugar, and brown sugar until smooth. Add the eggs one at a time, then stir in the vanilla extract until everything looks glossy.
Add the Dry Ingredients: Sift in the cocoa powder, flour, salt, and baking powder. Stir gently with a spatula until the batter comes together and no dry streaks remain.
Fold in Walnuts and Chocolate: Add the chopped walnuts and chocolate chips into the batter. Fold everything together carefully so the walnuts spread evenly through the mixture.
Transfer to the Pan: Pour the thick brownie batter into the prepared pan and spread it evenly with a spatula. Sprinkle a few extra walnuts and chocolate chunks over the top if you like.
Bake the Brownies: Place the pan in the oven and bake for about 30 to 35 minutes. The edges should look set while the center stays slightly soft for that perfect fudgy texture.
Cool Before Slicing: Remove the brownies from the oven and let them cool completely in the pan. This step helps the brownies firm up and gives cleaner slices.
Slice and Serve: Cut into squares and enjoy warm or at room temperature. The chocolate stays rich and gooey while the walnuts add a delicious crunch in every bite.
