Pre-heat the oven to 200 F and line two sheet trays with silicone mats. Crack the egg whites into a clean, bone dry bowl and use a hand mixer to whip them up into a foam for just 30 seconds. Add in the corn starch, gelatin powder and balsamic vinegar and whip it all together until the mixture starts to form soft peaks. Finally, pour in the sugar and continue to whip the meringue together until it forms stiff peaks. Transfer the meringue into a pastry bag fitted with a wide star tip.
Pipe the first rose right onto the sheet tray by starting in the center first and then continuing around it in a circle until you have a rose shape. Pipe about 15 onto each tray, depending on how big you make them. Bake the cookies for an hour and a half to basically dry the meringues on a low temperature. Turn off the heat and leave them in the oven for 8 hours to completely dry. Then transfer them into sealable containers or zip top bags until you want to give them out or serve them!