Beat the unsalted butter in a stand mixer/bowl until fluffy. Gradually mix in the confectioner’s sugar. Add the rest of the ingredients and combine until fluffy.
Once your cakes are cool (you never want to frost a warm cake), cut off the tops and bottoms using a long, serrated knife to ensure your cakes are flat.
Apply icing to the top of the first cake and stack the second on top. Repeat with the third cake.
Apply a thin layer of icing all around (crumb coat) and put the cake into the freezer for about 10 minutes.
Remove from fridge and apply more icing to the whole cake, saving 80 ml(1/3 cup) for rosettes.