Step 1

cut oranges into thin slices. Place them in a saucepan and add granulated sugar. Bring it over low heat, cover the pan, and cook for 1.5 – to 2 hours. Drain the candied oranges through a fine-mesh sieve to get the orange syrup. Add one tablespoon of Grand Marnier to the syrup and set aside. Cool the orange slices down.

Step 2

, preheat oven to 392 F/200 C. Using an electric mixer, whisk eggs and powdered (icing) sugar in a bowl, add the vanilla sugar. Bring the mix on a warm (not hot) bain-marie/ water bath to warm up the preparation and continue to whisk. Once the temperature of the eggs/sugar mixture reaches 113 F/45 C (warm to touch), remove the saucepan from the bain-marie/water bath and beat until the mixture doubles in size and cools down.

Step 3

Pour about three tablespoons of the cream-like mixture in a separate bowl with the melted butter in and mix. Add the sifted flour to the main mix and gently mix with a rubber spatula. Add the buttered mixture to the main preparation and combine, using the spatula.

Step 4

Butter and flour a cake pan 7 inches/18 cm in diameter. Pour the batter in the pan and bake for 20 minutes. Check the readiness of the biscuit with a knife: if it comes out dry, the biscuit is ready. Let cool on a wire rack.

Step 5

, bring milk to a boil. In a separate bowl, whisk egg yolks with granulated sugar until the mixture becomes whitish. Add the sifted flour and mix. Pour the boiling milk into the eggs’ mixture and stir. Bring it back in the saucepan and cook for 1 to 2 minutes, continually whisking until the cream thickens. Transfer the ready pastry cream in another bowl and beat with a hand whisk to cool down. Add the liquor Grand Marnier and vanilla extract.

Step 6

Butter a round cake pan 8 inches/20 cm in diameter. Sprinkle the bottom and sides of the pan with granulated sugar. Line the pan with orange slices, going in a circle and overlapping them in half. Refrigerate.

Step 7

Cut the rest of the candied oranges in small pieces and add them to the cooled pastry cream and mix with the spatula. Cover the cream with a plastic film in contact and refrigerate.

Step 8

Whisk whipping cream to get whipped cream. Add whipped cream to the cooled pastry cream and gently mix with the spatula. The diplomat cream is ready.

Step 9

fill an 8 inches/20 cm pan layered with the orange slices with half of the diplomat cream. Cut Genoise sponge in half in the direction of the thickness, using a serrated knife. Place a biscuit disk on top of the cream and soak with the orange syrup. Cover with the rest of the diplomat cream. Soak another biscuit disk with the orange syrup and cover the cream with the soaked surface down. Refrigerate the cake for at least two hours.

Step 10

To unmold, place the pan with the cake over medium heat for a few minutes. Place a serving plate on top of the cake and flip it over with the fast movement. Serve immediately or enjoy within the next 48 hours.