Prepare the Cake Layers:

1. Preheat your oven to 350°F (175°C). Grease and line 4-5 round cake pans.
2. In a large bowl, cream together the butter and sugar until light and fluffy. Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.
3. In a separate bowl, whisk together the flour and baking powder. Gradually add the dry ingredients to the wet mixture, alternating with the milk.
4. Divide the batter into separate bowls, one for each color you plan to use. Add a few drops of food coloring gel to each bowl, mixing until you achieve the desired pastel shade.
5. Pour the batter into the prepared cake pans and smooth the tops. Bake for 20-25 minutes, or until a toothpick inserted into the center comes out clean.
6. Allow the cakes to cool in the pans for 10 minutes before transferring to a wire rack to cool completely.

Make the Buttercream Frosting:

1. In a large bowl, beat the butter until creamy. Gradually add the powdered sugar, beating until smooth.
2. Add the vanilla extract and 4 tablespoons of heavy cream. Continue beating until the frosting is light and fluffy. If needed, add more cream for a smoother consistency.
3. If you want colored frosting, divide it into separate bowls and tint with food coloring gels.

Assemble the Cake:

1. Once the cake layers are completely cool, level the tops if necessary. Place the first cake layer on a serving plate and spread a layer of buttercream on top.
2. Continue stacking the layers, spreading buttercream between each one. Apply a thin crumb coat to the entire cake and refrigerate for 30 minutes.
3. After chilling, apply a final, smooth layer of buttercream to the cake.

Create the Drip Effect:

1. Melt the white chocolate in a microwave-safe bowl, stirring every 15 seconds until smooth. Add the heavy cream and mix until combined. Tint the chocolate with a pastel food coloring gel.
2. Using a spoon or piping bag, drip the colored chocolate around the edges of the cake, letting it cascade down the sides.

Decorate and Serve:

1. Add any remaining buttercream on top of the cake for decoration. Finish with sprinkles or decorative pearls if desired.
2. Serve immediately, or store in an airtight container in the refrigerator for up to 3 days.