Regarding the crust: Two cups of Graham crackers' crumbs One half cup (one stick) unsalted butter melted
Considering the layers: One packet Oreo cookies—roughly thirty-six cookies. One box brownie mix (plus eggs, oil, and water as specified on the box). Two cups miniature marshmallows
Set the temperature and get ready. I set my oven to 350°F and parchment paper lines a 9x 13-inch baking sheet. This greatly facilitates lifting the bars out later for slicing.
Make the crust. I toss the melted butter and graham cracker crumbs in a bowl until blended. To create a buttery basis, I press this mixture firmly into the bottom of the prepared pan.
Arrange the Oreos layerwise. I then completely line the graham crust with whole Oreos. I merely lay them down flat, side by side; I do not crush them. They make a great center layer and soften in baking.
Brownie batter mixing and pouring I follow the package instructions in preparing the packaged brownie mix. I then uniformly cover the Oreos with the batter, thereby covering them totally.
Cook I bake the bars until the brownie layer is set but still mushy in the middle, perhaps 30 to 35 minutes.
Add Toast and Marshmallows. I remove the pan from the oven once the brownies have baked and top with tiny marshmallows. I then put it back in the oven for another five to seven minutes, just long enough for the marshmallows to bubble up and turn just gently golden. .
Slice cool and neat. Before pulling the bars out and cutting them into squares, I let them cool totally in the pan. Clean cuts across the gooey layers are obtained with a sharp knife (and possibly some patience).