Preheat oven to 350F (180C). Line baking sheet with parchment paper. Grease 9-inch (23 cm) springform pan and line bottom with parchment paper.

In food processor, add flour, butter, granulated sugar, vanilla sugar and baking powder. Pulse until mixture resembles coarse crumbs. Add egg yolk and pulse until dough comes together.

On lightly floured work surface, roll out one-quarter of dough to 1/8-inch (3 mm) thickness. Using 2-inch (5 cm) rabbit-shaped cookie cutter, cut out 6 bunnies. Transfer to baking sheet.

Bake for 8 to 10 minutes or until lightly golden. Transfer cookies to wire rack to cool completely.

Press remaining dough evenly into bottom of springform pan; prick several times with a fork. Bake for 14 to 16 minutes or until golden. Let pan cool on wire rack for 10 minutes, then carefully remove cookie crust from springform pan and let cool completely.

Grease 9-inch (23 cm) springform pan and line bottom with parchment paper.

In large bowl, using handheld electric mixer, beat eggs for 1 minute or until fluffy. With electric mixer running, gradually add granulated sugar and vanilla sugar. Beat for 2 minutes.

Using sifter, add cornstarch, flour, cocoa and baking powder. Mix on low until just combined. Stir in butter until combined. Transfer to springform pan.

Bake for 22 to 26 minutes or until toothpick inserted in centre comes out clean. Let pan cool on wire rack for 10 minutes, then transfer cake to wire rack to cool completely.

Place cookie crust on cake plate and spread evenly with jam. Using serrated knife, cut cake horizontally in half. Place bottom half on top of jam. Top evenly with mandarins.

In large bowl, combine vanilla sugar and Whip It. Add cream and stir to combine. Using handheld electric mixer, whip mixture until stiff peaks form. Gently spread half of whipped cream over mandarins. Top with second cake layer, pressing down gently. Spread whipped cream over top and sides. Refrigerate until ready to decorate and serve.

Using icing pens, decorate rabbit cookies as desired. Sprinkle cake with pistachios. Arrange rabbit cookies and chocolate eggs on cake before serving.