• Do steps 1-3 of the Chocolate Mousse Filling before making the crust. (See Tip 1)

To Make the Crust

• Break the Oreo cookies into pieces and place them in a food processor fitted with the S-blade. Then, process the cookies until they are fine crumbs.
• Transfer the crumbs to a bowl and add three ounces of melted unsalted butter. Stir the butter into the crumbs with a fork until it resembles wet dirt.
• Transfer the moistened crumbs to a non-stick 9-inch tart pan with a removable bottom. Then, with your hands, press the crumbs into the bottom and sides of the tart pan to form the crust. Place the pan in the freezer for 15 minutes.

To Make the Chocolate Mousse Filling

• Place 7 oz of the Ghirardelli chocolate chips, 2 oz of cubed unsalted butter, and ½ cup of heavy whipping cream in a microwave-proof bowl.
• Microwave the bowl in 30-second increments, stirring after each heating, until the chocolate is melted. This should take one to one and a half minutes. Stir the mixture until fully emulsified and smooth.
• Add the vanilla extract and salt and stir them into the chocolate. Allow the mixture to cool to room temperature for about an hour, stirring occasionally so that it cools evenly.
• Place a metal bowl and a pair of beaters for an electric hand mixer in the freezer for about 15 minutes. Add two cups of cold, heavy whipping cream and powdered sugar to the frozen bowl. Place the frozen beaters in the electric hand mixer and beat the cream to stiff peaks.
• Add about half a cup of whipped cream to the cooled chocolate using an ice cream scoop. Whisk the whipped cream into the cooled chocolate.
• Add the remaining whipped cream to the chocolate mixture and use a rubber spatula to fold the whipped cream into the chocolate mixture.
• Add the chocolate mousse to the chilled crust. Use a rubber spatula to gently smooth out the chocolate mousse into an even layer. Then, place the filled pan in the refrigerator for two hours.

To Make the Chocolate Ganache

• Prepare the chocolate ganache after the tart has been in the refrigerator for about an hour. Place 13 ounces of Ghirardelli chocolate chips and 1 ¼ cups heavy whipping cream into a large microwave-proof bowl.
• Microwave the bowl in 30-second increments, stirring after each heating, until the chocolate is melted. This should take about a minute and a half. Stir the mixture until fully emulsified. Allow the mixture to cool to room temperature for about an hour, stirring occasionally so that it cools evenly.
• After the tart has been in the refrigerator for two hours and the ganache has cooled to room temperature, carefully remove the tart from the pan and place it on a large serving plate or a cardboard cake round.
• Then, add about a cup of ganache to the top of the tart. Quickly smooth out the ganache into a even layer covering the entire top of the mousse.
• Using an electric hand mixer, beat the remaining ganache for about 5-6 minutes until it's lighter in color and of a piping consistency.
• Place the whipped ganache in a piping bag with a large star tip. Pipe a border of large swirls of ganache around the edge of the tart and a large mound of swirls in the center. Refrigerate the tart for at least four hours before serving.
• Yield 12 servings