Preheat oven to 350°F/180°C.
Combine all ingredients except for chocolate chips and Oreos; mix well. Fold in the chocolate chips.
Pour batter into a 9x9-in. baking pan. Put one Oreo into each corner, but not too close to the edge. (When you use the cookie cutter, they will be in the center.) Cover the Oreos with the brownie batter.
Bake for about 35 minutes or until toothpick inserted comes out with minimal crumbs.
When it comes out of the oven, press it down using a spatula. Let cool. Cut into pumpkin shapes using a cookie cutter.
To decorate, melt the orange chocolate and spread over the brownies. Use an offset spatula to make wavy, vertical “pumpkin” lines. Melt the green wafers and use them as pumpkin stems. Melt about 1/2 c. of bittersweet chocolate for pumpkin faces; place the melted chocolate into a piping bag; use a tip if you like to create fun or scary faces.