Pour the sugar and water into a heavy-bottomed saucepan. Slowly bing to the boil, stirring occasionally with a wooden spoon.
Have a pastry brush and a cup of cold water to hand, and if any sugar crystals get stuck at the side of the pan, brush them down into the syrup. If you let them build up, they will attract all the other bits of sugar and the sugar won’t dissolve well.
The syrup is ready when it reaches 120°C. To check this, use a sugar thermometer if you have one, or use the ‘firm ball’ technique. For the latter, drop a teaspoon of the syrup into the cup of cold water.
If the syrup has reached 120°C, it will set into a firm ball, which can be squashed between your fingers. If the syrup forms a hard ball, like a hard-boiled sweet, it has reached too high a temperature for making Italian meringue – take it off the heat for 2 minutes o so to bring it back down to the appropriate temperature. If it just dissolves into the water, it is not yet hot enough.
While the syrup is boiling, whisk the egg whites to stiff peaks.
If you haven’t got a free-standing electric whisk, you will need 2 people to do the next stage as you need to keep whisking the whites as you pour the syrup over them. The syrup must be bubbling hot as it hits the whites in order to partially cook them.
So, carefully pour the bubbling hot syrup onto the whites in a steady stream, all the while continuing to whisk. Take care not to pour the syrup onto the wires or the whisk as it will quickly cool against the cold metal and can then harden and stick to the whisk.
Once you’ve added all the syrup, whisk hard and fast until the mixture is stiff, shiny and cooled, which will take 5-7 minutes. When it is ready, the meringue should not flow off the whisk when the whisk is lifted.
Use to top your meringue pie or pies or to fill your lemon waffles. If using as a pie topping, blow-torch the peaks or flash under a hot grill until golden.