Make cake in large cake pan....if you freeze it after cooking and cooling you can trim the cake in the center to look like a book with a v shaped slice down the center. Then add icing (much easier to design on the cake when frozen). The corner is a separately made section added on after all other icing is applied, then smoothed to look natural with a hot knife (place knife in hot water).
You can shape the corner section by making a triangular shape with the icing then place over the back of a teaspoon to curl. Let it harden, then slide to position you need on the cake. Hope this helps. Good luck.
What you've seen in probably fondant. You can buy it ready made (craft stores near the bridal section, probably, or with the Wilton things) and roll it out, cut it into shapes, color it like clay...It's a handy decorative thingie, but it isn't 'yummy' like frosting. If you're willing to sacrifice taste for looks, it's ok.
Add your voice to the conversation. Click here to answer this question.