Put all frosting ingredients in a large mixing bowl. Using an electric hand mixer or a stand mixer, beat all ingredients until smooth.
Put frosting in a piping bag with a plain circle tip.
Place a dollop of frosting in the middle of your cake board and lay down your first cake layer.
Put a flat, even layer of frosting on top of your second round (See above for detailed instructions)
Place your second cake round on top of the first one. Add another flat, even layer of frosting on top of the second layer.
Place your last cake round on top. Add another flat, even layer of frosting on the top layer.
Pipe straight lines of frosting down the side of your cake in even intervals. Using a bench scraper, gently scrape the frosting around the side of your cake to create the crumb layer of frosting.
Chill in the fridge 1-2 hours.