Cake batter:

1. Preheat the oven to 325°F (165°C) and line three 6-inch x 2.75-inch cake pans with parchment paper only in the bottom (or bake the batter all at once in a 4-inch deep pan or in three batches in the same pan).
2. In a large bowl, mix and sift the dry ingredients: flour, cornstarch, baking powder, and salt.
3. In the bowl of your stand mixer fitted with a whisk, beat the eggs with granulated sugar and vanilla on high speed for about 10-15 minutes until they triple in volume.
4. Meanwhile, whip the cold heavy cream with an electric mixer until it forms stiff whipped cream.
5. Gently fold in the mixture of dry ingredients with a spatula without overmixing.
6. Then add the whipped cream and incorporate it gently with a spatula until you get a homogeneous and smooth mixture.
7. Divide the batter into 3 parts and pour it into the prepared cake pans.
8. Bake the cakes together in the middle of the oven for 40-45 minutes without opening the oven door until they are golden on top. (check the baking by inserting a knife blade or toothpick into the center of the cake, it should come out clean without crumbs or liquid batter).
9. Let the cakes cool slightly in their pans before gently unmolding them and placing them upside down on a cake rack until they are completely cooled.

Vanilla filling:

1. Heat the milk with the vanilla bean or vanilla extract in a saucepan over medium heat until it simmers.
2. Meanwhile, whisk the sugar with the egg yolks and cornstarch in a large bowl.
3. Pour the hot milk over the egg yolk mixture and whisk to incorporate thoroughly.
4. Transfer the mixture back to the saucepan and cook over medium heat, stirring constantly with a hand whisk until the pastry cream thickens.
5. When it begins to boil, continue cooking for an additional 2 minutes.
6. Off the heat, add the butter pieces and vigorously stir to melt them, achieving a homogeneous mixture.
7. Pour the pastry cream into a small gratin dish, covering it with plastic wrap directly in contact with the surface. Place it in the refrigerator until it cools completely.
8. Just before assembling, whip the mousseline cream with the cold mascarpone for a good minute until it has a creamy texture.

Mascarpone frosting

1. Place all ingredients in a large container or in the bowl of your stand mixer, cold mascarpone cheese, cold heavy cream, powdered sugar and vanilla extract.
2. Leave the mixing bowl in the freezer for 10 minutes.
3. Beat with an electric whisk or a stand mixer fitted with the whisk attachment on medium low speed for about 2-3 minutes until smooth and firm.
4. Place the mascarpone whipped cream in the fridge for about 20 minutes before assembling.

Cake Assembly

1. If necessary, cut the bumps off the 3 vanilla cakes (and remove the crusts if you wish).
2. Assemble in a pastry ring adjustable to the size of the cakes, or in a 6x6" (15cm x 10cm) cake tin lined with plastic wrap to make unmolding easier.
3.  Place a first layer of cake and apply a boudin of mascaprone whipped cream to the outer edges, then fill the inside with mousseline cream and add a few fresh raspberries.
4. Cover with the second layer of cake and repeat until you reach the final layer.
5. Place the cake in the fridge for 20 minutes or 10 minutes in the freezer before finishing the frosting.
6. If necessary, whip again the mascarpone whipped cream at slow speed to firm it up a little and apply it with an angled spatula over the whole cake, smoothing with an angled saptula, decorate the top with the remaining mascarpone whipped cream and a star tip and garnish the top with fresh raspberries for decoration.
7. Serve immediately with homemade raspberry coulis, or store in the fridge.