Preheat the oven to 335°F. Grease and line three 6-inch cake pans or two 8-inch cake pans.

Warm the milk gently, then add the chopped white chocolate. Let it sit for 5 minutes.

Stir until the white chocolate melts into the milk. If needed, warm in short 10-second intervals, stirring between each one.

Stir in the vanilla extract, then let the white chocolate milk mixture cool until just above room temperature.

In a separate bowl, whisk together the flour, baking powder, and salt.

In a large mixing bowl, beat the softened butter and sugar together until light and fluffy, about 1–2 minutes.

Add the egg whites one at a time, mixing well after each addition.

Add one-third of the dry ingredients and mix on low until just combined.

Add half of the white chocolate milk mixture and mix again.

Continue alternating the dry ingredients and liquid mixture until everything is combined. Do not overmix.

Divide the batter evenly between the prepared cake pans.

Bake for 25–35 minutes, or until a toothpick inserted into the center comes out clean.

Let the cakes cool in the pans for 10 minutes, then turn them out onto a cooling rack.

Chill the cake layers before filling and frosting for easier assembly.

Add the raspberries and sugar to a medium saucepan over medium heat.

Cook until the raspberries break down and the mixture begins to bubble.

In a small bowl, mix the cornstarch with the cold water until smooth.

Stir the cornstarch mixture into the hot raspberry mixture.

Cook for 1–2 minutes, stirring constantly, until thickened.

Add the lemon juice and lemon zest, then cook for 1 more minute.

Transfer the filling to a heat-safe bowl or container.

Cover and let cool completely before using.

Place the chopped white chocolate in a heat-safe bowl.

Warm the heavy cream until it just begins to simmer.

Pour the warm cream over the white chocolate, making sure the chocolate is fully covered.

Let it sit for 5 minutes.

Stir gently until smooth and creamy. If small pieces remain, warm briefly in short intervals and stir again.

Set aside until needed.

In a large mixing bowl, combine the pasteurized egg whites and powdered sugar.

Mix on low to combine, then whip on high for 1–2 minutes.

Add the vanilla extract and salt.

Add the softened butter in chunks and whip for 8–10 minutes, or until the buttercream becomes light and fluffy. It may look curdled at first, but continue mixing.

Add the room-temperature or slightly warm white chocolate ganache.

Whip for another 2 minutes until smooth, light, and creamy.

For an extra smooth finish, mix on low for several minutes to reduce air bubbles.

Place the first chilled cake layer on a cake board or serving plate.

Spread a thin layer of white chocolate ganache over the cake.

Add a thin layer of white chocolate buttercream.

Pipe a ring of buttercream around the edge of the cake layer to hold the filling in place.

Add a layer of cooled raspberry filling inside the buttercream ring.

Place the next cake layer on top and repeat the ganache, buttercream, and raspberry filling layers.

Continue until all cake layers are stacked.

Apply a thin crumb coat of buttercream over the whole cake.

Chill the cake until firm.

Add the final layer of white chocolate buttercream and smooth the sides.

Decorate with fresh raspberries, raspberry filling, white chocolate shavings, or extra buttercream as desired.

Chill the cake for 30 minutes to set before slicing.