To cover a chocolate cake with icing, start by allowing the cake to cool completely. Then, spread a thin layer of icing over the top and sides of the cake to create a crumb coat. This will help to seal in any loose crumbs. Once the crumb coat has set, apply a thicker layer of icing to the top and sides of the cake, using a spatula to smooth it out. You can also use a piping bag to create decorative designs or borders with the icing. Allow the icing to set before serving the cake. **

Powdered sugar icing, also known as confectioners' sugar icing or glaze, is a simple and versatile icing made by combining powdered sugar with a liquid such as water, milk, or lemon juice. It is commonly used to drizzle over baked goods like cookies, cakes, and pastries to add a sweet and decorative finish. Powdered sugar icing can be flavored with extracts like vanilla or almond, and can be tinted with food coloring for a more decorative touch. **

The icing may not be hardening due to a few reasons. One possibility is that the ratio of ingredients in the icing recipe is off, such as too much liquid or not enough sugar. Another reason could be that the icing was not beaten for long enough to reach the desired consistency. Additionally, if the icing is exposed to high humidity or heat, it may have difficulty hardening properly. **

The cake icing is typically dry when it has hardened and no longer feels wet or sticky to the touch. This process can take anywhere from 1 to 4 hours, depending on the type of icing used and the thickness of the layer applied. To speed up the drying process, the cake can be placed in a cool, dry area with good air circulation. **

To make lemon icing, start by mixing powdered sugar and lemon juice in a bowl until smooth. You can adjust the consistency by adding more powdered sugar for a thicker icing or more lemon juice for a thinner icing. For a stronger lemon flavor, you can also add some lemon zest to the mixture. Once the icing is ready, you can drizzle it over your baked goods or spread it on top for a delicious lemony finish. **

To dry royal icing, you can simply leave the decorated item out at room temperature for several hours or overnight. You can also use a fan to speed up the drying process. Another method is to place the decorated item in a low-temperature oven with the door slightly ajar to allow moisture to escape. It's important to make sure the icing is completely dry before handling or storing the decorated item. **

Chocolate icing does not harden because it contains a high amount of fat, typically from butter or cream. This fat content prevents the icing from setting and hardening like a glaze or royal icing. Additionally, the presence of cocoa powder or melted chocolate in the icing also contributes to its soft texture. The combination of fat and moisture in the icing keeps it soft and spreadable, making it perfect for frosting cakes and cupcakes. **

The icing may not harden due to several reasons. One possible reason is that the ratio of liquid to sugar in the icing is too high, causing it to remain soft. Another reason could be that the icing was not cooked to the correct temperature, preventing it from setting properly. Additionally, if the icing was not allowed to cool for a sufficient amount of time, it may not harden as expected. **