How To Frost a Square Cake & Get Crisp Corners with Buttercream

  This step-by-step guide with photos will teach how to get crisp sharp edges on any square cake covered in buttercream

Sally Cake - BKeith Ryder

1. First, a square "cake" (sorry -- didn't have a real cake around to mess with). Slapped some icing on a square pan, and when I went to clean some icing away, I came up with a perfect square corner without even trying.
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So I took an intentional swipe at the corner to mess it up a bit so you could see what's what.
Sally Cake - BKeith Ryder
2. With your left hand, hold a spatula vertically in front of you so the right edge of the spatula is where you want the corner to be
BKeith Ryder
3. With another spatula in your right hand, start adding dabs of icing on the side of the cake running away from you, building up the corner against the "dam" spatula in your left hand.
square corners on a cake
4. Now gently slide the left hand spatula to the left, slowly bringing it away from the cake side to minimize the lift-off mark
square corners on a cake
5. Once the corners are built, I generally go back with my bench scraper and clean up the sides between the corners.
square corners on a cake
6. Same method works to do the corners on top of the cake too, just hold the left hand spatula horizontally (use a larger, elbow spatula to get a longer, cleaner edge)