Preheat your oven to 350°F (175°C). This ensures that your brownies bake evenly and achieve the perfect fudgy texture.
Line your 8x8 inch baking pan with parchment paper, allowing some overhang for easy removal later. This step is essential for fudgy brownies, as it helps prevent sticking.
In a large mixing bowl, combine the melted butter and cooking oil. Whisk them together until they are well blended. Add the granulated sweetener and mix until combined. Then, whisk in the eggs, one at a time, followed by the pure vanilla extract.
In another bowl, sift together the all-purpose flour, cocoa powder, and salt. Sifting helps to aerate the dry ingredients, resulting in a lighter brownie texture.
Gradually add the dry ingredients to the wet mixture, stirring gently until just combined. Be careful not to overmix, as this can lead to dense brownies. The batter should be thick and fudgy.
Pour the brownie batter into the prepared baking pan, spreading it evenly. Bake in the preheated oven for 20-25 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs. Remember, underbaking slightly is key to achieving that fudgy texture.
Once baked, remove the brownies from the oven and let them cool in the pan for about 10 minutes. Use the parchment overhang to lift them out of the pan and let them cool completely on a wire rack before slicing into squares.