Heat the raspberry purée in a saucepan.

Whisk together the fruit pectin and sugar, then add them to the hot purée.

Stir constantly over low heat until the sugar mixture has fully dissolved.

Increase the heat and bring the jam to a boil.

Simmer for 7-10 minutes, until thickened.

Remove from the heat.

Pour the hot raspberry jam directly into a 16 cm cake ring, then freeze.

Set aside a small amount of jam for decorating the cake.

Prepare the vegan buttermilk: combine the oat milk and vinegar, then let it thicken for 5 minutes.

Combine all the dry ingredients in a large mixing bowl.

Add the vegan buttermilk and melted vegan butter to the dry ingredients, then whisk (or use an electric mixer) until smooth.

Preheat the oven to 170°C.

Line a baking sheet with parchment paper, then spread the batter to a thickness of 1 cm.

Bake for 20-25 minutes.

Let the sponge cool before cutting.

Refrigerate if you don't need it right away.

Place all the ingredients in a saucepan, then bring to a boil.

Transfer to a container and set aside.

Whisk together 1/3 of the lukewarm oat milk (not hot), the egg yolks, sugar, vanilla, and cornstarch in a bowl.

Stir carefully until the cornstarch is completely dissolved.

Pour the cream mixture into the remaining lukewarm milk and cook over medium heat, whisking constantly until thickened.

Remove from the heat.

Transfer the pastry cream to a mixing bowl and cover with plastic wrap.

Let cool to room temperature, about 18-20°C.

Whisk the cooled pastry cream, then add the softened vegan butter in three additions.

Continue whisking until light and silky.

Keep in mind that the mousseline will split if the pastry cream is still warm.

Use immediately, or keep covered in a cool place, but not in the refrigerator.

Cut out 2 sponge discs using a 16 cm cake ring.

Cut an acetate sheet to fit the cake ring.

Set an 18 cm x 4.5 cm cake ring lined with acetate on a cake board.

Place one sponge disc in the center of the cake ring, brush it with syrup, then arrange the halved raspberries side by side all around the inside edge of the ring.

Cover the raspberries with mousseline cream, then spread the cream up against them to coat the sides of the ring.

Spread a 1 cm-thick layer of mousseline cream over the sponge, then top with pieces of sliced raspberries.

Top with the second sponge disc and brush it with vanilla syrup.

Add the final layer of mousseline cream to fill the top of the cake ring.

Level off the excess cream with a spatula, then refrigerate for at least 1 hour.

Remove the cake ring, but leave the acetate sheet in place.

Place the frozen raspberry jam disc in the center.

Decorate by arranging the sliced raspberries in overlapping circles between the jam disc and the edge of the cake.

Finish with three whole raspberries in the center, a few drops of slightly warmed clear neutral glaze or raspberry jam, and some toasted slivered almonds.

Refrigerate after decorating.

Remove the acetate lining just before slicing the cake.