Preheat oven to 220°C (430°F) or 200°C (390°F) for fan-forced ovens. Use paper towels with lemon juice or vinegar to clean the bowls, whisk, and utensils. Line a large baking tray with non-stick baking paper (parchment paper) for the meringues. Do not grease the tray or the paper because we will use the meringue mixture later to 'glue' the paper to the tray to keep it in place. Place a star tip for the pumpkins or a round tip for the ghosts and place the bags over a tall glass.
Line a separate small baking tray with baking paper and place the sugar in the middle. Place this sugar tray in the oven for 7 minutes or until the outside edges of the sugar will melt slightly. Avoid leaving the heated sugar on the bench top for too long before adding it into the meringue. Reduce the heat to 120°C (250°F) or 100°C (210°F) for fan-forced ovens. Leave the oven door open as this will help the oven temperature go down faster.
Whilst the sugar is in the oven, start whisking the egg whites in the stand mixer using the balloon whisk attachment. Start on low speed and gradually increase the speed. Once the egg whites start to foam and small bubbles appear, increase the speed to medium high. Whisk until the egg whites are at stiff peaks, then increase the speed to the highest setting and slowly add the heated sugar in a teaspoon at a time, pausing for a few seconds in between to allow the eggs to get back to stiff peaks.
Once all the sugar is all added, stop the mixture and scrape the sides of the bowl. Continue to mix at the highest speed for 5 to 8 minutes. Test the meringue mixture by placing a small amount between your fingers. If it's still gritty, keep mixing for a little longer. Once the meringue is smooth and the sugar has dissolved, add in 1 or 2 drops of orange food colouring (if making pumpkins). Whisk it at high speed for a few seconds until the colour has combined evenly.
Optional - For the pumpkin, use a skewer to apply orange food colouring into the piping bag lengthwise. Place half of the meringue in the piping bag and pipe 1cm size ghosts or pumpkins on the prepared tray. You can pipe them close to each other but not touching as they shouldn't expand too much. Bake them for 20 to 30 minutes or until they are dry to the touch, and easy to lift from the baking paper. Leave the meringues cool completely in the oven, with its door ajar. This usually takes 3 to 4 hours, or you can leave it overnight. Draw faces on the pumpkins and ghosts.