Place the egg whites in a mixer and begin mixing on low speed. Gradually add the first 150 grams of sugar as the egg whites begin to foam.
Increase the mixer speed and add the remaining 300 grams of sugar in two or three additions. Continue whipping for about 15 minutes until the mixture is glossy and forms stiff peaks.
Transfer the meringue to a piping bag with a star tip and pipe your desired shapes onto a parchment-lined baking sheet.
Bake at 248°F (120°C) for 2 hours until set and crisp. Let cool and store in an airtight container.