Line the base of a 22cm springform cake pan with plastic wrap or baking paper, making sure to leave a 2cm overhang. This will help make removing the finished cake much easier.

In the bowl of a stand mixer fitted with a whisk attachment, combine the thickened cream, mascarpone, egg yolks, sifted powdered sugar, and vanilla bean seeds. Whisk on high speed until the mixture is stiff and well combined. Once finished, cover and chill in the refrigerator until ready to use. I find chilling the bowl beforehand helps the cream whip up even better.

In a medium bowl, combine the juice from 2 oranges and the Grand Marnier. Briefly dip half of the ladyfinger cookies into the mixture, ensuring they are moistened but not soggy.

Place the soaked ladyfingers (from Step 3) in a single layer at the base of your prepared cake pan. Spread one-third of the chilled mascarpone mixture (from Step 2) over the ladyfingers, and then top with one-third of the mango slices. Repeat layering with more soaked ladyfingers, another third of the mascarpone mixture, and another third of the mango slices. Finish with a final layer of the mascarpone mixture, reserving the last third of the mango slices for decoration later. Cover and chill the assembled cake for at least 2 hours, or until firm.

While the mangomisu chills, prepare the raspberry sauce. In a small pan over medium heat, combine the granulated sugar and 2 tablespoons of water. Stir continuously until the sugar dissolves. Add the raspberries and lemon juice, then lightly crush the berries with a spoon. Remove from heat and allow to cool completely. Once cool, pass the sauce through a sieve set over a bowl to strain out the seeds, then chill until ready to serve. For a more intense berry flavor, I sometimes let the raspberries simmer a few extra minutes.

Once the mangomisu has set, carefully remove the sides and base of the cake pan and transfer the cake to a serving platter. Arrange curls of the reserved mango slices (from Step 4) decoratively on top. Slice and serve each portion with a generous drizzle of the chilled raspberry sauce from Step 5.