Preheat your oven to 350°F (175°C) and grease and flour two 9-inch round cake pans.

In a medium-sized bowl, whisk together the flour, baking powder, baking soda, and salt.

In a large mixing bowl, cream together the butter and sugar until light and fluffy.

Add the eggs one at a time, beating well after each addition, then mix in the vanilla extract.

In a separate bowl, combine the milk and sour cream until smooth.

Gradually add the dry ingredients to the butter mixture, alternating with the milk-sour cream mixture, and fold in the melted white chocolate.

Divide the batter between the prepared cake pans and bake for 25-30 minutes or until a toothpick comes out clean.