Put crème fraiche and heavy cream in a large mixing bowl. Stir in sugar and vanilla, cover and refrigerate.
In a medium saucepan toss rhubarb and strawberries with the sugar and ground vanilla powder. Add wine and bring to a gentle simmer over medium-low heat. Cook, stirring occasionally and gently until the liquid is a little creamy and rhubarb is tender but the pieces are still largely intact, about 15 – 20 minutes. Let cool completely, then stir in rose water.
With a whisk or handheld electric mixer, whip the cream mixture until it’s fluffy and holds semi-stiff peaks. Spoon some of the rhubarb mixture into the bottom of a large bowl or the bottoms of 4 – 6 glass bowls or glasses. Top with a layer of cream. Repeat layers until you’ve used everything, finishing with a layer of rhubarb. Cover and refrigerate until cold. Add a sprinkle of freshly grated nutmeg if desired, before serving and/or garnish each with a strawberry.