Frosting a Cake
1. Place one of the bottom layers onto the cake stand or platter. Transfer 1/3rd of the buttercream into a piping bag fitted with a round tip. Pipe concentric circles onto the layer, and with a small offset spatula smooth out the buttercream. Place the matching top of the cake layer onto the buttercream, gently pressing down to adhere the layer onto the frosting.
2. Repeat the process with the other cake layers.
3. With the entire cake assembled, spread a thin coat of buttercream over the top and the sides to seal in the crumbs; this is called a crumb coat. Place into fridge to set the crumb coat; about 15 minutes or until buttercream is firm to the touch.
4. Add the final layer of buttercream over the crumb coat, making sure not to scrape against it while smoothing out the frosting over the top and sides.