Prepare the Cake:

1. Preheat oven to 350°F (175°C). Grease and line three 8-inch round cake pans.
2. In a medium bowl, combine flour, baking powder, and salt.
3. In a large bowl, cream butter and sugar until light and fluffy. Beat in eggs one at a time, then mix in vanilla.
4. Alternate adding the dry ingredients and milk to the wet ingredients, beginning and ending with dry.
5. Divide batter evenly among pans and bake for 25–30 minutes. Cool completely.

2. Make the Ganache:

1. Heat heavy cream until steaming but not boiling. Pour over chopped white chocolate in a bowl.
2. Let sit for 3 minutes, then stir until smooth. Allow to cool to dripping consistency.

3. Make Buttercream:

1. Beat butter until creamy. Gradually add powdered sugar, heavy cream, and vanilla, mixing until smooth and fluffy.

4. Assemble the Cake:

1. Frost and stack the cake layers with buttercream. Spread a thin crumb coat, chill for 30 minutes, then apply a smooth outer layer.
2. Pour ganache over the chilled cake edges, letting it drip naturally. Decorate as desired.