Gâteau d’Orange

To make the buttercream: In a small saucepan mix the sugar and cornstarch and add the cream. Stir with a whisk until there are no lumps. Place over medium hat and stir frequently until the mixture thickens and comes to a boil. Cook, stirring, for 3 to 3-1/2 minutes. Pour into a small bowl and add the chopped white chocolate. Let stand 30 seconds, then stir to blend. Let cool to room temperature; cover with plastic wrap and refrigerate overnight.

To finish the buttercream, put the chilled mixture into a mixing bowl and beat until soft peaks form. Beat in the butter, a tablespoon at a time with a balloon or whisk attachment. Continue beating until the buttercream is smooth and has at least doubled in volume. Add the vanilla, Grand Marnier, and zest and beat again until completely blended.

To make the meringues: Line baking sheets with parchment paper and trace three 8-inch circles on the paper. Preheat the oven to 200 F. Grind the almonds to fine meal with a little sugar. With the mixer on medium-high, beat the egg whites until foamy. Gradually beat in the sugar,cornstarch, and extracts. Continue beating until glossy peaks form. Fold the ground almonds into the mixture by hand with a spatula. Fill a pastry bag fitted with a large plain tip with meringue and pipe a tight spiral on each of the circles, leaving no spaces between the rows. Smooth the tops with a cake spatula. Bake 1-1/2 to 2 hours, until the meringue circles have dried. You may turn off the oven and leave the pans on the racks to cool overnight. When cool, trim 1/2 inch from the diameter and flatten off the tops of the meringues with a knife so the meringues will be flat when stacked.

To assemble: Place a dab of buttercream in the center of a nine-inch cake plate and top with a meringue disc, pressing to adhere the disc. Generously cover the meringue with buttercream. Top with another meringue and generously cover with buttercream. Top with the final meringue and spread the top and sides with buttercream. Place in a large clean plastic bag, inflate the bag, and seal (this protects the cake without letting anything touch the icing.) Refrigerate overnight.

To make the creme anglaise: Whisk the yolks in a small bowl until smooth. Set aside. Combine the sugar and half-and-half in a small saucepan and cook over medium-high heat until the mixture comes to a boil. Stir a large spoonful of the hot mixture into the egg yolks. Whisking gently, slowly pour the remaining hot mixture into the egg yolks. Put the cream-yolk mixture back into the saucepan and cook, stirring constantly, until slightly thickened. Remove from heat, pour into a heat-proof bowl, and place the bowl into a larger bowl filled with ice. Stir mixture often to chill evenly. When cool, mix in the Grand Marnier.

To serve: Cut the orange slices in half (not necessary if you are using mandarin slices). Remove the cake from the refrigerator and slice into 12 portions. Place on dessert plates and ladle a large spoonful of creme anglaise around each. Put the whipped cream into a pastry bag fitted with a large fluted tip and pipe a curved strip of whipped cream on each portion. Garnish each with half an orange slice and a few mint leaves.