Preheat the oven to 350 degrees F.

Prepare two 8x8 or 9x9-inch square baking pans with parchment lining the bottom and all four sides. Lightly spray with cooking spray. Mix up the brownie batter according to the package directions. Split the batter evenly between the two pans and smooth out the tops with a spatula.

Bake the brownies for 15-20 minutes, until a skewer comes out with moist crumbs, but not wet batter. Let the brownies cool completely in the tins. Meanwhile, let the pints of gelato soften in the fridge for 30 minutes.

Once cool, use the parchment flaps to carefully slide the brownies out onto a wire cooling rack. Then, use two pieces of plastic wrap to line one of the brownie tins. Arrange the plastic wrap in a cross shape to line the sides of the tin.

Slide one of the brownies off of the wire rack. Then, invert the plastic wrap-lined pan over the brownie on the wire rack. Then flip the the brownie into the pan.

Use a silicone spatula to spread and even layer of the gelato over the upside down brownie in the pan.

First, flip that brownie onto a sheet of plastic wrap so it is now upside down (be sure there is a good amount of plastic wrap on all sides of the brownie). Then, to minimize its travel distance and handling, slide the other brownie tin upside down, under the plastic wrap.

Now, grab the plastic wrap on the side of the brownie farthest from the gelato. Carefully lift it up slightly. Take a breath, let it out, and in one smooth motion, flip the brownie over onto the gelato.

Use the plastic wrap we used to flip the brownie to spread across the top, then pull the sides of the plastic wrap lining the baking tin up and over the top of the Pistachio Gelato Brownie Sandwich, tightly sealing it up.

Place the Pistachio Gelato Brownie Sandwich in the freezer for at least 3 hours.

When the sandwich comes out of the freezer, we want to work kinda quick so the gelato doesn't get too melty. So have your pistachios chopped and your chocolate sauce handy. Flip the sandwich out onto the counter, then flip it back over. Then un-peel the plastic wrap and discard it.

Make one cut vertically down the center of the sandwich. Then, slice it horizontally in the center to make quarters, then cut each quarter in half. This will yield 8 sandwiches.

Squeeze some chocolate sauce on each sandwich and use an offset spatula or knife to spread the chocolate sauce, end to end on each sandwich.

Then sprinkle the chopped pistachios over the top.

Now, tightly wrap each bar in plastic wrap. Put the wrapped bars on a sheet tray and place back in the freezer for at least 2 hours or until ready to serve.