Preheat your oven to 350°F. Grease and line two 9-inch round cake pans with parchment paper.
In a large bowl, beat together the cake mix, milk, oil, eggs, and sour cream until smooth and thick, about two minutes. Gently fold in the white chocolate. Divide the batter evenly between the pans and smooth the tops. Bake for 20 to 25 minutes, until a toothpick comes out clean. Let the cakes cool completely.
Beat the butter until creamy. Gradually mix in the powdered sugar, then add the vanilla and 4 tablespoons of cream. Beat until light and fluffy, adding more cream if needed. Tint with pink food coloring to your favorite shade.
Place one cake layer on a serving plate. Spread with a generous layer of buttercream and sprinkle with Valentine’s sprinkles. Top with the second layer and frost the top and sides. Chill for 15 to 20 minutes to set.
Heat the cream until steaming, then pour it over the white chocolate. Let it sit for a few minutes, then stir until smooth and glossy. Once slightly cooled, spoon the ganache around the edges of the cake for a natural drip effect. Finish with more sprinkles on top.