Get ingredients:
Attach the paddle to the mixer.
Add to mixer mixing bowl:
Mix on medium-high speed until smooth (about 7 minutes ).
While waiting for the butter, sift into large mixing bowl:
Set mixer to low speed.
Add the dry ingredients to the mixer mixing bowl, 1/4 at a time.
Add to the mixer mixing bowl:
For a thinner consistency (best for covering a cake smoothly and piping text), add another 1 tbsp milk.
Mix on low speed until uniform (about 30-60 seconds ).
Optionally, add food colouring while the icing is still in the mixing bowl. Mix with the mixer or stir with a spoon until consistent.
Assembling a cake
Get tools:
If you are assembling the cake on a cake turntable and planning to transfer the cake to a box/stand/plate later:
Optionally, place four long rectangular sheets of parchment paper around the top edges of the surface to create the outline of a square.
Place the first cake on the surface.
If the cake will contain a filling, such as a fruit compote:
Using a piping bag with no tip (or a 1/2" tip), pipe a circle of icing on top of the cake about 1/4" from the edges.
Scoop the filling onto the cake.
Spread the filling out evenly so it covers the entire top of the cake.
Using an offset spatula, scoop some icing on top of the filling.
If the cake will not contain a filling:
Using an offset spatula, scoop about 1-2 cups icing on top of the cake.
Using an offset spatula, spread the icing as evenly and flatly as possible until it's about 1/2" thick.
Place the second cake on top of the first cake so that the flatter part of the second cake is at the top.
Optionally, if the sides of the cake are not even, use a serrated knife to trim the sides.
Crumb coat
The purpose of the crumb coat is to lock in the crumbs (to prevent them showing on the outer layer), fill in cracks, and shape the cake. It doesn't need to look pretty, but getting the right shape is important.
Using a pastry brush, very gently brush the cake to remove any loose crumbs.
Using an offset spatula, scoop some icing on top of the cake.
Using an offset spatula, swipe the icing across the top of the cake to create a thin layer.
Using an offset spatula, apply a thin layer of icing to the sides of the cake, starting at the bottom.
Hold the offset spatula vertically so it is just touching the side of the cake at a 45-90 degree angle.
While keeping the spatula still, rotate the cake turntable to scrape excess icing off the sides and create a smooth surface. Apply some light pressure.
Using the offset spatula, swipe excess icing around the top edge of the cake towards the middle.
Using the offset spatula, smooth the top of the cake.
Place the cake in the fridge for about 30 minutes (or the freezer for about 15 minutes ) (or until the icing is firm and dry and doesn't come off when you touch it).
Icing a cake
Remove the cake from the fridge (or freezer).
Scoop the remaining icing on top of the cake.
Repeat the steps for the crumb coat, using a thicker layer of icing (about 1/8" thick) so the cake doesn't show through.
Remove the cake from the fridge (or freezer).
Decorate.
Place the cake in the fridge for about 30 minutes (or the freezer for about 15 minutes ) (or until the icing is firm and dry and doesn't come off when you touch it).
Remove the cake from the fridge (or freezer).
Slowly pull the parchment paper out from under the cake.
Transfer the cake (including the cake round) from the turntable to the box/stand/plate.