Preparing the Vanilla Cake Layers

1. Preheat your oven to 350°F (175°C). Grease three 8-inch round cake pans, line the bottoms with parchment paper, and grease the paper.
2. In a medium bowl, whisk together the cake flour, baking powder, and salt. Set aside.
3. In a large bowl, use an electric mixer to beat the butter on medium-high speed until creamy, about 1 minute. Add the granulated sugar and beat until light and fluffy, about 3-4 minutes. Scrape down the sides of the bowl as needed.
4. Add the eggs one at a time, beating well after each addition. Beat in the vanilla extract.
5. On low speed, add the flour mixture in three additions, alternating with the milk, beginning and ending with the flour mixture. Mix just until combined after each addition. Be careful not to overmix.
6. Divide the batter evenly among the prepared pans. Bake for 23-26 minutes, or until a toothpick inserted into the center comes out clean. For the most level cakes, bake with cake strips around the pans.
7. Allow the cakes to cool in the pans for 10 minutes, then remove from pans and transfer to wire racks to cool completely.

Making the Raspberry Filling

1. In a medium saucepan, combine raspberries, sugar, and lemon juice. Cook over medium heat, stirring occasionally, until berries break down and release their juices, about 5-7 minutes.
2. In a small bowl, whisk together cornstarch and water to create a slurry. Stir the slurry into the raspberry mixture.
3. Continue cooking, stirring constantly, until the mixture thickens, about 2-3 minutes. The filling should coat the back of a spoon.
4. Remove from heat and transfer to a bowl. Cover with plastic wrap, pressing it directly onto the surface to prevent a skin from forming. Refrigerate until completely cooled.

Preparing the White Chocolate Buttercream

1. Place chopped white chocolate in a microwave-safe bowl. Microwave in 30-second intervals, stirring between each, until completely melted and smooth. Allow to cool until just warm to the touch.
2. In a large mixing bowl, beat the butter on medium-high speed until pale and creamy, about 3-4 minutes.
3. Pour in the cooled melted white chocolate and beat until well combined.
4. Add the powdered sugar gradually, beating on low speed at first, then increasing to medium-high. Mix in the vanilla extract and salt. Add heavy cream one tablespoon at a time until desired consistency is reached. Beat on high speed for 3-4 minutes until light and fluffy.

Assembling the Cake

1. Use a long serrated knife to level the tops of the cake layers if needed.
2. Place one cake layer on a serving plate or cake board. Pipe a ring of buttercream around the edge to create a dam for the raspberry filling.
3. Spread half of the raspberry filling inside the buttercream dam. Be careful not to overfill.
4. Place the second cake layer on top and repeat the process with a buttercream dam and the remaining raspberry filling.
5. Top with the third cake layer. Apply a thin layer of buttercream all over the cake to seal in the crumbs. Refrigerate for 20-30 minutes to set.
6. Once the crumb coat has set, apply the remaining buttercream all over the cake, creating a smooth finish. For a more rustic look, create swirls with an offset spatula.
7. Use a vegetable peeler to create white chocolate curls from the reserved chocolate bar. Gently place these around the top edge of the cake.
8. Arrange fresh raspberries on top of the cake, along with mint sprigs if desired, for a stunning presentation.