The secret to perfect frosting is to apply a “crumb coat” and let it chill before slabbing on a second layer. This will keep all those pesky crumbs from getting mixed up in the frosting.
Have cake, icing, long flat spatula, an off-set spatula and a pastry brush (or a very clean soft basting brush) ready to frost cake. If you have a cake turn table, this will help greatly! If not, you can turn over a large pan and use this to give your cake and plate some height.
Make sure icing is room temperature. Never use hot icing! It won’t set and can weaken your cake.
If filling the cake with the same icing you will be using to frost, make sure the icing doesn’t come all the way to the edges of the cake tier. If the frosting is too close to the edges it will seep out and make a real mess.
If you’re using a fruit filling, use a pastry bag to pipe a ring of icing all the way around the tier being filled making sure it’s just slightly inside the edge of the tier. This will help keep the fruit filling on the cake layer and not outside the icing boundary.
Once you’ve assembled your cake, begin with a crumb coat. A crumb coat is a thinner layer of icing meant to even out the surface of your cake, pick up an crumbs and help you get a base for the final frost. It serves as a primer coat, so to speak. Take the soft bristled pastry brush and brush your cake off very gently. This will take off all the loose crumbs that could make your icing bumpy.
Ready to frost: Take a nice portion of icing and put it on top of your cake. While turning your cake slowly smooth the icing from the center of the cake towards the edges. Try to be very gentle and not pick up too many crumbs or tear the cake.
When you reach an edge, you will need to pick up a bit of icing and spread it carefully around the circumference of the cake. Be very careful when icing the sides, this is where a lot of crumbs are! Be gentle and try not to tear the cake. If a crumb is too big, carefully pick it out of your icing so it doesn’t leave a bump. Use that upside down pan or cake turntable to slowly turn your cake to get all the sides. I find an off-set spatula works best for the sides. Also, should you notice anything uneven, this is the time to pad that uneven spot with a bit more icing to make your cake appear symmetrical.
Once the cake has been crumb coated with a thin layer of icing, put it in the fridge for about 30-45 minutes. This will harden up your crumb coat and make it easier to frost the show coat.
Once the icing has set, return it to your turntable/cake pan and prepare for the show coat.
Begin frosting just as you did for the crumb coat, with a portion of icing right in the center of the top of the cake. Working carefully towards the edges. Then frost the sides carefully.
If you want your cake icing to be perfectly smooth… no marks whatsoever, with an almost fondant appearance, then put it back in the fridge. Let it set up for another 30-45 minutes. This seems to work best with butter creams and heavy type icings.
To smooth the icing: use a small off-set spatula dipped in a cup of hot water. Then wipe off the water from the spatula and very very lightly go over the frosting to smooth away any bumps. Use a light hand, you don’t want to pull up any icing! Keep dipping the spatula in the warm water and wiping it off then smoothing. Repeat with the fridge and spatula until the cake is smooth.
If you want a design in your frosting: simply use your spatula or whatever tool you choose to make your icing swirled, peaked or in whatever pattern you like. Again, be careful, use a light hand. You don’t want to tear or pull up crumbs!