Preheat the oven according to the brownie recipe directions. Line two 9 x 9-inch baking dishes with parchment paper.
Prepare the brownie batter and evenly divide it between the two pans. Bake for 12 to 14 minutes or until a toothpick comes out clean. Remove the brownies from the oven and allow them to cool down completely.
While the brownies cool, remove the ice cream from the freezer and allow it to soften at room temperature.
Remove one brownie square from the pan and set it onto a flat surface. Use a knife to remove the crispy edges.
Slice both squares in half lengthwise to create 2 rectangles. Slice each rectangle into 5 vertical strips. *Watching the video makes this step clear.
Remove the lid from the carton of ice cream and use a serrated knife to cut the entire carton in half lengthwise.
Place both halves onto the brownies in the baking dish and remove the carton- the ice cream should be soft enough that it easily separates from the container but isn’t dripping.
Spread the ice cream over the brownies with a spatula and top it with the other section of slice brownies (this will create ten sandwiches total).
Cover the baking dish with plastic wrap and freeze for 4 hours.
Once frozen, remove the brownie ice cream sandwich from the freezer and trim the excess ice cream edges. Cut into 10 individual sandwiches and serve.
Wrap the leftovers with parchment paper and freezer in a large zip bag.