Sift almost all of the confectioner's sugar (175g). Beat the egg whites and the salt until stiff. Gradually add the confectioner's sugar until the egg whites are very firm and shiny. Quickly work in the corn starch and vinegar.
Fill the egg whites into a pastry bag with a star-shaped tip and, on a cookie sheet lined with parchment paper, form 4 circles (about 4" or 10 cm across) and fill them in with the egg whites mixture. Line the circles' perimeters with spiky dollops of the egg white mixture so that they form a border.
Bake the meringues in a preheated oven at 350 degrees F, then reduce the temperature to 250 degrees F and bake for another 45 minutes. Let the meringues cool down.
Wash, clean, thinly peel and finely chop the rhubarb. Combine the rhubarb, the juice and sugar in a saucepan, cook until very soft and let the mixture cool down.
Whip the cream adding the Whip It, the remaining confectioner's sugar and the rosewater. Gently fold the rhubarb into the cream and chill the mixture.
Before serving clean and quarter the strawberries. Divide the cream evenly among the meringues and garnish with strawberries.