Step 1: Prepare the Cake

1. Preheat your oven to 350°F (175°C). Grease and line three 8-inch round cake pans.
2. In a bowl, whisk together flour, baking powder, and salt.
3. In a separate large bowl, cream butter and sugar until light and fluffy. Add eggs one at a time, mixing well after each addition. Stir in vanilla extract.
4. Gradually add the dry ingredients to the wet mixture, alternating with milk, beginning and ending with the dry ingredients.
5. Fold in the melted white chocolate until just combined. Divide the batter evenly among the prepared pans.

Step 2: Bake the Cake

1. Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.
2. Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.

Step 3: Make the Raspberry Filling

1. In a saucepan, combine raspberries, sugar, cornstarch, and water. Cook over medium heat, stirring constantly, until thickened.
2. Allow the filling to cool completely before assembling the cake.

Step 4: Prepare the Frosting

1. Beat butter until creamy. Gradually add powdered sugar, one cup at a time, mixing well after each addition.
2. Mix in the melted white chocolate, vanilla extract, and heavy cream. Beat until smooth and fluffy.

Step 5: Assemble the Cake

1. Place one cake layer on a serving plate. Spread a layer of frosting, followed by a thin layer of raspberry filling.
2. Repeat with the second layer. Top with the final cake layer and frost the top and sides of the cake.
3. Garnish with fresh raspberries and white chocolate shavings as desired.