Grease the baking pan with cooking oil spray and line with parchment paper.
Sprinkle a little flour on the halved walnuts.
Combine melted butter, oil, and sugar together in a bowl and whisk well for about a minute, this gives a nice crackly top.
Add the eggs and vanilla and beat for another minute until it gets a pale and lighter color
Add flour, cocoa powder, walnuts, and salt gently stirring the dry ingredients until just combined
Do not overbeat at this point as it will affect the texture of the brownies.
Pour the batter into the greased pan and smooth the top out evenly
Bake for about 25 minutes until the center of the brownies no longer jiggles and on testing, with a toothpick, it comes out dirty
.Cool in the pan and slice into small brownie squares.
Video
Notes
Whisk well for the crackly top: To achieve that shiny, crackly top, be sure to whisk together the melted butter, oil, and sugar thoroughly for at least one full minute. Don’t skip it!
Combine the batter gently after the flour addition: Once you add the flour, mix just until combined. Overbeating at this stage can lead to tough, cakey brownies instead of the soft, fudgy texture that you are looking for.
Line your pan: Line your baking pan with parchment paper, leaving some extra hanging over the sides. This makes it easy to lift the brownies mess-free without sticking.
Watch the bake time: Brownies are done when a wooden toothpick inserted in the center comes out with a few moist crumbs or a little sticky batter and not clean. This ensures a gooey, fudgy inside.
Cool before slicing: Let the brownies cool completely in the pan before cutting. This helps them set properly and gives you clean, neat squares without crumbling.