Preheat the oven to 350 degrees and spray an 8 x 8 pan with non-stick spray. Set aside.
Make the brownie layer
In a large bowl, add the sugar, flour, cocoa powder, salt, baking powder, and chocolate chips. Mix it up (I use a spatula) so it is well combined.
1 cup granulated white sugar, ½ cup all purpose flour, ⅓ cup unsweetened cocoa powder, ½ teaspoon salt, ¼ teaspoon baking powder, ½ cup chocolate chips
In a measuring cup, add in the oil then eggs, and vanilla. Mix up the wet ingredients with a fork.
2 large eggs, ⅓ cup vegetable oil, 1 teaspoon vanilla extract
Pour the wet ingredients into the dry ingredients and stir with the spatula until just combined.
Spread the mixture into the prepared 8 x 8 pan.
Make the cookie layer
In a medium bowl, add the butter, sugar, and brown sugar. Mix with a fork until fully combined.
¼ cup unsalted butter, ¼ cup granulated white sugar, ¼ cup light brown sugar
Add in the beaten egg and vanilla. Mix until combined.
1 large egg, ½ teaspoon vanilla extract
Add in the flour, salt, baking soda, and chocolate chips. Mix until combined, making sure all dry ingredients are fully incorporated.
1 cup all purpose white flour, ½ teaspoon salt, ½ teaspoon baking soda, ½ cup chocolate chips
Use your hands to flatten pieces of the dough and lay on top of the brownie layer. Fit the pieces together, like a puzzle, until you have a fairly even layer covering the brownie batter.
Bake for at least 30-35 minutes then check on it. You want the cookie layer to get golden brown, but not burn, while cooking all the way through. After 35 minutes I turned my oven down to 325 then let it bake another 10 minutes. A toothpick inserted in the center should come out clean (as long as you don't hit a chocolate chip!).
Let cool for at least 10 minutes (more like 20 to be safe, or put it in the fridge to speed it along) before attempting to cut it into bars.
Notes
Makes an 8x8 pan so depending on how generous you cut them, you should have at least 9 brookies.