Step 1: Prep the Baking Sheet

1. Preheat the oven to 375°F (190°C).

2. Line an 18×13-inch rimmed baking sheet with foil, leaving a 2-inch overhang on at least two sides. Coat with nonstick cooking spray.

   • Tip: Use a half-sheet pan for the right size. Foil overhangs make lifting easy; spray well to prevent sticking.

Step 2: Assemble the Cookie Layer

1. Arrange 24 chocolate sandwich cookies (e.g., Oreos) on half of the baking sheet in 6 rows of 4 cookies.

2. Press and spread two 16.5-ounce packages of softened chocolate chip cookie dough over the Oreos, covering half the baking sheet to form one giant cookie.

   • Tip: Use clean hands or a spatula to spread dough evenly. Press gently to embed Oreos without breaking them.

Step 3: Assemble the Brownie Layer

1. Prepare the brownie batter according to the package directions (typically mixing with eggs, oil, and water).

2. Pour the batter into the empty half of the baking sheet.

3. Arrange 24 vanilla sandwich cookies (e.g., Golden Oreos) in 6 rows of 4 on top of the brownie batter, pressing them in gently.

   • Tip: Spread batter evenly to match the cookie layer’s thickness. Press Golden Oreos lightly to avoid sinking.

Step 4: Bake

1. Bake at 375°F for 20-23 minutes, until a toothpick inserted in the chocolate chip cookie and brownie portions comes out with just a few crumbs.

2. Let cool completely in the pan on a cooling rack (about 2 hours).

3. Freeze the pan for 30 minutes to firm up.

   • Tip: Check both sides for doneness; don’t overbake for fudgy brownies. Cool fully to prevent cracking when flipping.

Step 5: Assemble the Ice Cream Sandwich

1. Use the foil overhangs to lift the giant cookie from the baking sheet. Carefully flip it onto a cutting board, ensuring it doesn’t bend or crack. Peel off the foil.

2. Line the baking sheet with plastic wrap.

3. Place the chocolate chip cookie half (Oreos facing up) on the prepared baking sheet.

4. Working quickly, spread 4 cups softened vanilla ice cream evenly over the cookie half, reaching all edges. Smooth the top and sides.

5. Place the brownie half (Golden Oreos facing down) on top of the ice cream, pressing gently to adhere.

6. Fold the plastic wrap around the assembled sandwich to hold its shape.

   • Tip: Soften ice cream just enough to spread (not melted). Work fast to keep it firm. Use an offset spatula for smooth ice cream.

Step 6: Freeze and Cut

1. Freeze the assembled sandwich for at least 6 hours, or overnight, until hardened.

2. Use a warm serrated knife to trim the rough edges into a 12×16-inch rectangle.

3. Cut crosswise into 24 sandwiches (6 rows of 4).

4. Optionally, roll edges in red, white, and blue sprinkles for a 4th of July flair.

5. Serve immediately or wrap individually and freeze.

   • Tip: Warm the knife under hot water and dry between cuts for clean slices. Serve quickly to prevent melting.