In a bain marie over low heat, add your egg whites and heat whisking constantly for 2-3 minutes or until the egg whites are warm but not cooking. This process will kill any bacteria in the eggs making them safe to use when raw.

In the bowl of a stand mixer fitted with a whisk attachment (thoroughly cleaned and grease free) whisk the egg whites on high speed until foamy, around 2 minutes. (You can also do this using a handheld electric mixer).

With the mixer on medium-low speed, gradually add the sifted powdered sugar one spoonful at a time.

Once all of your sugar is incorporated, add the lemon juice and whip on high speed until thickened, about 3 minutes.

The icing at this stage will be at a good consistency for flooding cookies. If you want it stiffer for frosting a cake or writing on cookies add more powdered sugar until you get the consistency you desire.

Place the icing into a bowl and cover with cling wrap. Make sure the cling wrap is in direct contact with the icing as this will prevent it from hardening while you are waiting to use it.

Use it straight away or store in an airtight container at room temperature for up to 2 weeks or in the fridge for up to 4 weeks.