Rose Petal and Yogurt Mousse

For many years now, we have tried to cultivate heirloom fragrant roses in our garden on Kea—Rosa damascena and related varietals—but our dry climate and poor soil have made it very difficult to produce enough rose petals to make jam. Fortunately, good-quality organic dried rose petals, together with good rosewater (see Sources), have helped me make plenty of jam to flavor this light yogurt mousse that our guests love. High-quality jars of Bulgarian, Fre