Heat the oven to 200C/180C fan/gas 6. Put the caster sugar in a small roasting tray lined with baking parchment. Shake to level out the sugar and heat in the oven for about 5 mins until hot but not melting. This helps stabilise the egg whites and give a smooth and glossy meringue.

Put the egg whites and cream of tartar into the bowl of a stand mixer. Whisk slowly at first, gradually increasing the speed until the egg whites are at the stiff peak stage, about 5 mins. It’s important not to over-whisk the egg whites. Remove the sugar from the oven as soon as the eggs whites are stiff.

Turn the oven down to 110C/90C fan/gas 1/4, leaving the door ajar to help it cool down quickly – the meringues need to be baked at a lower temperature.

Turn the mixer up to full speed and start adding the sugar one tablespoon at a time. You want the egg whites to maintain their volume as you keep adding sugar, so if you see it starting to collapse, stop adding sugar and allow the mixture to stiffen and rise before adding the rest, a spoonful at a time.

Once all the sugar has been added, keep whisking until you have a stiff and glossy mixture. It’s ready to use when it holds its shape, about 2-5 mins after you add the last of the sugar. You should also be able to see peaks in the mixture as you remove and upturn the whisk.

To add colour to your monsters, you will need to paint your piping bags. This mixture will make enough for two piping bags – one green, and one purple – but feel free to choose your own monster colours, and even mix them up by painting stripes. Turn your piping bags inside out. Place the bags over jugs or bottles so that they hold themselves up. Paint a thick layer of food colouring from the tip of the piping bag to halfway down the bag. Invert the bags, then carefully spoon your meringue into piping bags – one batch should fill two bags, shaking the mixture down to the bottom of the bag. Try to get rid of any big air bubbles you can see at this stage, but don't be too rough with the mixture.

Cut some baking parchment to the size of your baking trays. Cut off the bottom inch of the piping bag (about a 50p-sized hole) and squeeze small dollops on to the corner of your baking trays to stick the parchment down.

Hold the piping bag with both hands, placing your dominant hand at the top of the bag and your other hand halfway down the bag. Hold the bag steady, about 2cm above the tray and squeeze the bag from the top to start forming the body of your monsters. Stop squeezing once the meringue hits the tray. Lift the piping bag a little without creating a break between the meringue on the tray and the meringue left in the piping bag. Drop the bag back down again and squeeze gently to form the top part of the monster’s body.

Repeat until you have piped all of your mixture, working quickly as the mixture will loosen over time. Bake for 40-50 mins until crisp on the outside and soft in the middle. Leave to cool on the baking trays.

If you want to make your own googly eyes, do this at least 24 hrs in advance. Make 100g stiff royal icing, colouring a quarter of this black using black gel colouring. Put the white and black icing into two separate piping bags. Use scissors to snip a little hole at the tip. Carefully pipe white dots onto a parchment-lined baking tray, then leave them to set. Once dry, use the black icing for the pupils. Pipe different-shaped eyes – some big, some small, or perhaps three adjoining. Leave to set overnight until they lift off the baking parchment easily. Use more icing to stick the eyes onto the meringues. Once set, will keep for two weeks in a cool dry place in a loosely covered container.