Prepare the cake mix (or mixes) according to the package directions. If you want a two layer cake, divide the mix out evenly between two prepared 9" pans and bake according to the package directions. If you want more layers, prepare the second boxed mix and repeat.
Let the cakes cool completely. While the cakes are cooling, prepare the frosting.
To the bowl of a stand mixer, add the sugar & butter. Start by beating the two together on low speed, increasing the speed a little bit as they come together.
Pour in the pureed strawberry and whip the mixture until everything's come together and a smooth buttercream frosting has emerged.
Run a butter knife around the edge of one of the cake pans to 'release' the cake. Turn it out onto your desire surface. I recommend this being the surface you're going to serve it on- either a plate or a cardboard cake circle.
Spread a thin layer of the strawberry buttercream evenly out over the cake. Repeat until you've reached your desired number of layers- either 2, 3, or 4. The less layers, the thicker the frosting filling layer can be.
Frost the outside of the cake completely with the strawberry buttercream, getting it as smooth as possible without pulling cake or crumbs away.
Transfer the cake to a freezer, and let chill for 15-20 minutes.
Heat the candy melts in a medium sized sauce pan until they've begun to melt, stirring occasionally.
Once they've begun to melt stir in the warm cream, and continue to stir together until a uniform smooth, glossy consistency forms. Remove the ganache from heat, set aside.
Take the cake out of the freezer, and set on wire baking racks set over top of a rimmed baking sheet. Pour the ganache on top, in the center of the cake.
Use an inverted spatula to gently spread the ganache over the surface and towards the edges of the cake. Stop once a bit's begun to drip over all around. Sprinkle sprinkles evenly out over the cake, if using.
Let the cake sit & the ganache set. Once set, the cake can be covered and stored for up to 24 hours, or sliced & served immediately.