Preheat the oven to 350 F, and position a rack in the center of the oven. Line a 9x9 inch square baking pan with parchment paper so the paper comes up all 4 sides of the pan.
Place one of the rounds of cake on a cake decorating turntable, and frost the top of the cake. Fill and frost with three more rounds of cake so that you have four stacked rounds of cake.
Now frost the sides of the cake with a thin crumb coat of buttercream. This tallest one will be the hardest to assemble; keep your fingers on top of the cake to steady it as you frost the sides so it doesn't topple over.
Now cut out a small portion of cake from the top layer, and fit one of the tea light candles inside.
Frost the sides of the cake with a final coat of buttercream, using a bench scraper to sweep it around the sides and smooth it out as much as possible. It doesn't need to look perfect, since it will be covered with dripping white chocolate.
Carefully slide a small offset spatula under the cake, again keeping your fingers on top of the cake to steady it, and transfer it to a serving plate. Frost the top edge of the cake, leaving the candle unfrosted.
Now repeat the above steps with the remaining rounds of cake and buttercream, making a medium pillar candle with three rounds of cake and a short pillar candle with two rounds of cake.
Place the plate with the frosted cakes in the refrigerator to chill for 15 minutes.
White Chocolate Ganache
In a microwaveable bowl, combine the white chocolate chips or chopped chocolate and the cream. Microwave for two minutes on 50% power, then stir until smooth. Microwave for 20-30 more seconds on 50% power, if needed. For a less yellow color, add a few drops of "bright white" gel food coloring (optional).
Use a spoon to drizzle the white chocolate ganache around the edges of the cakes, letting it drip down the sides. Be careful not to get the white chocolate on the candles. Then place the plate of cakes back in the refrigerator to chill for a few minutes before adding more drips.
Continue to add layers of white chocolate drips, chilling the cakes for a few minutes each time, in between layers, until you've used up all the ganache and the cakes are covered in drips.
Before serving, light the candles! You'll get about 9 servings from these cakes.