For the Tart Crust: Combine the flour, sugar, and salt in a medium sized mixing bowl. Place the cold butter between two pieces of grease proof paper (like waxed paper) and pound it until it’s about 1/4” thick, using a rolling pin or kitchen mallet.

Using your fingers, work the butter into the flour mixture quickly, until the mixture is sandy. Using a rubber spatula or a bowl scraper, mix in the egg until the mixture is a cohesive dough. Using your fingers, gently and deftly becomes a ball, then pat it into a disc and wrap tightly with plastic wrap. Place it in the refrigerator for at least 2 hours, or up to three days.

When you are ready to bake it, remove the chilled dough from the refrigerator. Preheat the oven to 375°. Let it soften slightly, then roll out on a floured surface into a round 1/4”inch thick. Roll it back over the pin to transfer it to a round 9” tart pan. Dock the crust (prick all over with a fork), line it with parchment paper and fill with pie weights, beans, or sugar. Bake for 15 minutes, then remove the parchment with the weights. Bake for another 10-15 minutes, or until the crust is golden all over. Let it cool completely before filling.

For the White Chocolate Mousse: In a small bowl, beat the 2 egg yolks with two tablespoons of sugar until smooth. Heat 1/2 cup of whipping cream in a small saucepan over medium heat until barely simmering, then slowly pour it into the eggs while whisking quickly. Return the mixture to the pan and cook over low heat, stirring constantly with a rubber spatula until it is thick, then remove from the heat. Stir the chopped white chocolate in until it has melted. Transfer the mixture to a small bowl, then chill for two hours.

Beat the remaining 1/2 cup of whipping cream until stiff peaks form, then carefully fold into the custard until it’s completely mixed. Pour it into the cooled crust, then let it set in the refrigerator for 2 hours.

For the Milk Chocolate Mousse: Repeat the method for the white chocolate mousse, and pour it over the white chocolate layer in the crust. Again, let it set for 2 hours

For the Ganache Layer: Chop the dark chocolate and place it in a heat proof bowl. Heat the 3/4 cup of whipping cream in a small saucepan or in the microwave until gently simmering. Pour it over the chopped chocolate, then let it sit for 10 minutes. After that, stir it gently until the mix becomes cohesive and smooth. Pour it over the top of the milk chocolate mousse, then refrigerate for a couple of hours or until the ganache sets.

For the Chocolate Garnish (Optional): Using a sharp chef’s knife, lightly rub the back of a bar of chocolate with your hand to soften it slightly. Place the blade of the knife almost flat against the chocolate, angling and pressing it down slightly, and carefully pull it towards yourself, skimming off a curl of chocolate. It may shatter, but the fragments can still be very pretty. Arrange the curls in any pattern on the top— I placed mine all around the edges, but they could also be very pretty piled in the middle or scattered across the top.