Grease three 8-inch round cake pans with butter. Line the bottom of each cake pan with parchment paper and grease the paper as well. If you don’t feel like cutting parchment paper rounds, cut three 4-inch parchment paper strips and place each strip in a cake pan so it hangs over the edges a few inches. This will make it easier to lift the krispie layers out of the pan. Set aside.
(We’ll make three layers of krispie treats, one at a time. You can either make the melty marshmallow mixture in a small saucepan over medium heat or in the microwave.)
- First make the chocolate marshmallow mixture. In a small bowl in the microwave or small saucepan melt together one portion of butter and all of the chocolate. Add the marshmallows to the melted butter and chocolate and microwave for 1 minute to 1:30 seconds or stir in the saucepan over low heat until melted.
- Place 4 cups of rice krispie treats to a medium bowl. Pour the melted chocolate marshmallow over the cereal. Add a pinch of salt and stir until evenly coated and combined. Press into one of the prepared pans. (Wet your fingertips and press the sticky krispies into the edges of the pan.) Place in the refrigerator while you make the other layers.
- Make the vanilla layer in the same way, adding a splash of vanilla extract. Place in the refrigerator while you make the final strawberry layer.
- Melt the final third of butter and marshmallows until soupy, sticky and smooth. Dust the strawberry powder (and a few red food coloring drops) atop the melted marshmallow mixture and whisk until well combined. If you’re using food coloring, mix in a few more drops than you think you need. Stir in the cereal and press into the prepared pan like the other two cake layers.
- Allow all of the cake layers to rest in the refrigerator for 30 minutes until just set.
- While the cakes set, make the buttercream. In a medium bowl with electric hand beaters, beat together softened butter, powdered sugar, and a splash of milk. Whip until smooth. Add any food coloring you might like. Spoon buttercream into piping bag with a Wilton 14 star tip.
- To assemble the cake remove the layers from the refrigerator. Place the chocolate layer on a cake plate or cake stand top side up. The krispies will still be slightly soft – that’s great. Remove the vanilla layer from the pan and place top side up on the chocolate layer. Use your clean hands to press and mold the layers together. Do the same with the final strawberry layer.
- Dot the cake with buttercream. Add a border to the bottom edge of the cake. Add cherries or strawberries. Add sprinkles or candles. Allow the cake to chill for 30 minutes before serving.
- To store, cover loosely in plastic wrap and store either at room temperature or in the refrigerator.