Line a 9-inch springform pan with plastic wrap. Place in the freezer.

Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.

In a small bowl, combine the crushed chocolate sandwich cookies and melted butter. Stir until well combined.

Spread the cookie crumb mixture evenly on the prepared baking sheet. Bake for 7-8 minutes. Let cool completely, then break into bite-sized pieces for the cookie crunch.

Soften the first quart of chocolate ice cream for 15-20 minutes. Spread it evenly into the bottom of the prepared springform pan. Freeze for 30 minutes to 1 hour until firm.

Gently warm the hot fudge sauce in the microwave for about 15 seconds to make it spreadable. Stir well and spread it evenly over the frozen chocolate ice cream layer.

Sprinkle the prepared cookie crunch pieces evenly over the hot fudge layer. Freeze for 1 hour until firm.

Soften the second quart of chocolate ice cream for 15-20 minutes. Gently mix in the chocolate chunks.

Spread the chocolate ice cream and chunk mixture evenly over the cookie crunch layer. Cover and freeze for at least 4-6 hours, or preferably overnight, until completely solid.

Just before serving, prepare the whipped cream frosting. Chill a mixing bowl and whisk attachment (or handheld mixer beaters) in the freezer for at least 30 minutes.

In the chilled bowl, beat the cold heavy whipping cream, powdered sugar, and clear vanilla extract on high speed until stiff peaks form (about 3-4 minutes).

To frost the cake, work quickly. Release the outer ring of the springform pan and carefully remove the plastic wrap.

Place the ice cream cake on a serving plate or cake board. Frost the top and sides of the cake with the whipped cream. You can use a spatula for a smooth finish or pipe decorative swirls using a piping bag with a star tip.

Sprinkle the chopped brownie pieces over the top of the cake.

Drizzle with chocolate syrup if desired. Return the cake to the freezer until ready to slice and serve.