Creme diplomat combines the richness of pastry cream with the lightness of whipped cream, creating an ideal filling for delicate pastries like cream horns. Make traditional creme patissiere (pastry cream) first, allowing it to cool completely - warm pastry cream will deflate whipped cream. Once cold, fold in whipped cream in stages to maintain airiness. The ratio is typically two parts pastry cream to one part whipped cream. Creme diplomat holds its shape better than plain whipped cream but remains lighter than pastry cream alone. It must be refrigerated and used within a day. Flavor with extracts, coffee, citrus, or other aromatics added to the pastry cream base before folding in whipped cream.