Step 1: Prepare the Cake Layers
Preheat your oven to 350°F (175°C).
Grease and line two 8-inch round cake pans with parchment paper.

In a medium bowl, whisk together the flour, baking powder, and salt.
In a large bowl, beat the butter and sugar until light and fluffy, about 3 minutes.
Add the egg whites, one at a time, beating well after each addition.
Mix in the vanilla extract.

Alternate adding the flour mixture and the milk to the butter mixture, beginning and ending with the flour.
Stir in the sour cream until just combined.

Divide the batter evenly between the prepared pans and smooth the tops.

Step 2: Bake the Cake
Bake for 25-28 minutes, or until a toothpick inserted into the center comes out clean.
Let the cakes cool in the pans for 10 minutes, then transfer to a wire rack to cool completely.

Step 3: Make the White Chocolate Frosting
Melt the white chocolate in a microwave-safe bowl in 20-second intervals, stirring between each until smooth. Let cool slightly.

In a large bowl, beat the softened butter until creamy.
Add the melted white chocolate and beat until combined.
Gradually add powdered sugar, one cup at a time, beating well after each addition.
Add vanilla extract, a pinch of salt, and enough heavy cream to reach a fluffy, spreadable consistency.

Step 4: Assemble the Cake
Place one cake layer on a serving plate or cake stand.
Spread a thin layer of white chocolate frosting over the top.
Spoon raspberry jam over the frosting, gently spreading it out, and sprinkle fresh raspberries if using.

Place the second cake layer on top.
Apply a thin crumb coat of frosting all over the cake and chill for 20 minutes.

Frost the entire cake with a thick, even layer of white chocolate frosting.

Step 5: Decorate
Garnish the cake with fresh raspberries, white chocolate curls, or edible flowers for a stunning finish.

Step 6: Slice and Serve
Use a sharp knife to cut clean slices and enjoy your dreamy creation!