Liquid glucose cannot be used alone to ice a cake, but it can be added to a fondant icing recipe to soften the texture and prevent crystallisation. Use liquid glucose to make a dough-like fondant, which never hardens and remains pliable. Thinning the fondant creates a pourable version for icing cakes rather than draping the icing.
In the bowl of an electric mixer, combine 1/2 cup vegetable shortening, 1/2 cup butter and 1 tsp clear vanilla extract. Beat together to cream the shortening and butter.
Turn the mixer down to medium-low or low speed and beat in the icing sugar 1 cup at a time to prevent splattering.
Add 2 tbsp milk and 4 tbsp liquid glucose to the icing mixture and turn the mixer speed to medium-high. Beat until light and fluffy. This adaptation uses liquid glucose instead of corn syrup, which you can use as a substitute.
Cover the bowl with a damp towel until you are ready to use the icing. Dip a spatula inside the icing and cover the cake with a thin layer. Refrigerate the cake for one hour.
Remove the chilled cake from the refrigerator. Apply a second coating of buttercream icing to the cake, or pour a fondant coating over the chilled and thinly iced cake following the procedure in section 2 below.
Combine together 2-1/2 cups granulated sugar, 1/2 cup water and 4 tbsp liquid glucose in a saucepan. Clip the candy thermometer to the side of the pan. Stir the ingredients as you heat this mixture over medium heat until it reaches 114 degrees Celsius. Substitute liquid glucose in any recipe calling for corn syrup, as in this adaptation, since corn syrup consists mainly of glucose.
Transfer the icing ingredients to a food processor and allow to cool for 30 minutes. after the mixture cools to 60 degrees Celsius, insert the thermometer and process the ingredients for 3 minutes.
Refrigerate the iced cake for one hour before applying the poured fondant.
Place the pourable fondant icing into the saucepan and place it on the stove, but leave the heat off. If the fondant cools too much, you'll need to rewarm it. Place the candy thermometer inside the fondant. Wait for it to read between 100 and 105 degrees Fahrenheit before applying it to the cake.
Place the chilled and iced cake atop parchment paper. Pour the pourable fondant over then entire cake. Pick up the pan or plate holding the cake and tilt it to allow the fondant to evenly coat the sides. Flatten out the fondant by smoothing it with a metal spatula. Refrigerate the cake for 20 to 30 minutes and apply a second layer of fondant, if desired.