Step 1

Preheat the oven to 350 degrees. Prepare an 8x8 inch baking pan by spraying with nonstick spray or lightly greasing with oil. Line the pan with a strip of parchment paper so that some is overhanging on two sides. Set aside.

Step 2

In a food processor, blend up the graham crackers and sugar until they reach a fine crumb consistency. Pulse in the melted butter until all of the crumbs are evenly coated . Add the graham cracker mixture into the prepared pan. Press down on the crumbs with the bottom of a cup or a spatula to ensure the crust is very compact and even.

Step 3

Bake the crust in the oven for about 15-20 minutes, or until the edges look golden brown and the crust looks slightly puffed up. Set aside to cool slightly.

Step 4

Meanwhile, in a medium bowl, add the vegetable oil, sugar, eggs, and vanilla extract. Mix the ingredients together with a whisk until just combined. To the mixture, add the cocoa powder, flour, salt and baking powder. Continue to mix with the whisk until the batter looks even with no more streaks of cocoa powder. Fold in the chocolate chips. The batter will be thick and fudgy.

Step 5

Gently pour the brownie batter over the crust in the pan, and carefully use a knife or small offset spatula to spread it evenly over the crust. Bake in the oven for 30 to 40 minutes, until everything looks set and the middle is no longer jiggly.

Step 6

Remove the brownies from the oven and set the oven to broil, leaving a rack in the middle of the oven to ensure the parchment paper won't burn. Evenly sprinkle the mini marshmallows on top of the brownies, and place them under the broiler for about 2 minutes, checking frequently.

Step 7

Let the brownies rest for at least 30 minutes at room temperature before cutting and serving. To ensure clean slices of the brownies, run your knife under hot water first and wipe the knife between each slice.