In a mixer fitted with the paddle attachment, beat butter and cream cheese until smooth, about 2 minutes.
Slowly add powdered sugar, followed by vanilla and milk. Mix until light and fluffy.
MAKE THE KRISPY TREATS:
Prepare 4 (6-inch) round and 1 (4-inch) square cake pans with non-stick cooking spray.
Place cereal in a large bowl. Set aside.
In a large pot over medium heat, melt butter. Add in mini marshmallows and stir constantly until melted.
Add melted marshmallow mixture to cereal and mix until well combined.
Allow to cool 5 minutes, then mix in 1 cup of sprinkles.
Divide the mixture evenly between the 5 prepared pans, then add 1/4 cup sprinkles to the top of the square pan.
Spray hands with non-stick cooking spray and press down until the layers are tightly packed. Set in the fridge for 20 minutes, then remove from pans.
Place one round krispy treat layer on a cake stand. Cover the top with about 1/2 cup frosting.
Repeat with the second and third layer.
Add the fourth layer and frost the top of the cake. Bring the frosting down the sides of the cake. Use an offset spatula to scrape the top and edges and smooth the frosting. The frosting should not cover the entire cake. Some of the krispy treat layers will show through.
Set in the fridge for at least an hour.
MAKE THE GANACHE:
Place 1 cup turquoise chocolate in a medium bowl.
In a medium saucepan, bring 1/2 cup cream to a boil over medium heat. Pour over turquoise chocolate and whisk until smooth and shiny. Let cool about 20 minutes until thickened but still runny.
Use a spoon to drip chocolate down the sides of the cake and cover the top.
Chill cake in fridge 30 minutes to 1 hour.
Place 1 cup pink chocolate in a medium bowl.
In a medium saucepan, bring 1/2 cup cream to a boil over medium heat. Pour over pink chocolate and whisk until smooth and shiny. Let cool about 20 minutes until thickened but still runny.
Remove cake from fridge and use a spoon to drip chocolate down the sides of the cake and cover the top.
Sprinkle remaining 1/4 cup sprinkles over the top of the cake.
MAKE THE DECORATION:
Place the remaining 1/2 cup turquoise chocolate in a small microwave-safe bowl and melt at half power in the microwave, stirring occasionally. Dip 6 marshmallows halfway into the pink chocolate. Let dry on a sheet of parchment paper.
Repeat process with the remaining 1/2 cup pink chocolate and the remaining 6 marshmallows.
Cut the remaining 4-inch square layer of krispy treats into 1-inch squares.
ASSEMBLE THE CAKE:
Top the cake with krispy treat squares and chocolate-dipped marshmallows. Store, covered, in fridge for up to 3 days.