Neat, sharp corners on a fondant cake make a subtle difference that shows a designer's level of skill and perfectionism. Cake designs in which sharp corners are especially important include baby block cakes or cakes designed to resemble boxes, but any cake design looks better with this technique. Cake corners and edges tend to be rounded when fondant is simply laid over the cake and smoothed out without much extra effort. Fondant's pliability allows you to wedge it between two fondant smoothers and achieve sharp corners.
Wait for the fondant to set and harden slightly for about half an hour after covering the cake. When the fondant is slightly hardened, it won't tear as easily but you can still shape it at the corners.
Place one fondant smoother on top of the cake, with part of it extending over the cake's edge. Place a second fondant smoother on the side of the cake toward the top so it butts against the overhanging part of the first fondant smoother.
Push the two fondant smoothers tightly together as you push them along the top edge of the cake. In addition to running side to side along the top edge, push the second fondant smoother from bottom to top to pull the edge tight. Repeat this as much as needed to achieve a crisp edge around the top.
Position the two fondant smoothers on either side of a cake corner. Push them toward the corner until the two smoothers meet.
Hold one fondant smoother so it slightly overhangs the right side of a corner. Position a second fondant smoother on the left side of the corner. Push this second smoother along the side until it butts up against the first smoother at the corner. Switch positions so the first fondant smoother overhangs the left side of the corner with the second smoother on the right side. Glide the second smoother along the right side until it butts against the first smoother. Repeat this process at each corner of the cake.
- Fondant smoothing tools are designed specifically for smoothing out fondant and sharpening the corners, but you can use any similar object. Try two bench scrapers, commonly used for working with dough, or even two sheets of super-thin acetate, which produce even sharper edges and corners.