In a food processor, or by hand with a rolling pin and large ziploc bag, crush the chocolate sandwich cookies until a fine crumb is formed.

Transfer the crumbs to a large bowl and add 4 tablespoons of melted butter. Stir until the butter is fully mixed and a crumbly texture has formed. Set aside.

Grease a 9 inch tart tin with a removable bottom with butter. Pour the cookie mixture into the tin.

Using a spoon, your hands, or a combination of the two, gently press the mixture into the bottom and sides of the pan until an even layer has formed.

Refrigerate the crust in the tin for 30 minutes to one hour.

Beat the 4 large egg yolks in a large bowl with a hand mixer for 3 to 4 minutes on a medium/high speed.  The eggs will thicken and turn into a paler color.

Slowly blend in the ¼ cup of granulated sugar and set the bowl aside.

Heat 1 cup of the cold heavy whipping cream in a saucepan over medium heat until it’s just hot, but not boiling. Remove from the heat when small bubbles begin to form around the edge of the pan.

Remove the pan from the heat and ladle half a cup of the cream into the egg mixture while continuously whisking.  This will raise the temperature of the eggs, without scrambling them (called tempering). Whisk until combined.

Pour the tempered egg mixture into the saucepan with the rest of the cream and place over medium-low heat. Continue to cook, gently stirring for 3 to 4 minutes until the mixture coats the back of a spoon. To test, dip a plastic or wooden spoon to the mix, and carefully run your finger or another tool across the spoon.  If a path is left, the cream is ready.

Remove the pan from the heat and add the chopped semisweet and bittersweet chocolate to the cream and eggs.   Stir until the chocolate has melted and fully incorporated. Add the 2 teaspoons of vanilla extract and stir to combine.

Let the mixture cool in the pan at room temperature until no longer warm to touch, about one hour.

After the chocolate mix has cooled, beat 1 ¼ cup of whipping cream with a hand mixer until stiff peaks are formed, starting slow and  increasing the speed as needed.

Add ⅓ of the whipped cream to the chocolate, gently folding it in to keep as much air as possible.  Once incorporated, add the remaining whipped cream to the mix, gently folding in to keep as much air as possible.

Transfer the mousse to a piping bag if desired and refrigerate until ready to use.

Remove the crust from the fridge and distribute the fresh raspberries across the bottom of the tart, leaving ½-1 inch of space between each, saving a few for decorating the tart if desired.

Pipe or spoon the chocolate mousse over the raspberries, using a rubber spatula to bring the mousse to the edges of the crust and smooth the top.

Refrigerate for 1 to 2 hours in the tart pan.

In a large bowl, whip the cold whipping cream, cocoa powder, and powdered sugar with a hand held mixer, beginning at a slow speed and slowly increasing the speed to medium/high.  Mix until stiff peaks are formed.

Transfer the chocolate whipped cream to a piping bag fitted with a star-tip nozzle, refrigerate until ready to use.

Add the freeze-dried raspberries to a high-powered blender and blend until a fine dust  is formed.

Remove the tart from the refrigerator and take it out of the tin and onto a serving plate. Snip the end of the piping bag of chocolate whipped cream and pipe small rosettes across the top of the tart. Decorate with extra raspberries if  desired and powder the raspberry dust across the top.

Refrigerate until ready to serve, slice, and enjoy!