To prevent whipped cream from separating over several hours, you need to add a whipping cream stabilizer. A stabilizer helps the cream hold piped rosettes and stiff peaks when presentation is key. While you can buy a commercial stabilizer to do this (check the baking aisle of your nearest supermarket or a bakery supply store), you can make your own quite easily.
To stiffen 1 c. (250 mL) of heavy cream, set the cream momentarily aside. Soak ½ tsp. (2.5 mL) unflavored gelatin in 1 tbsp. (15 mL) cold water in a very small bowl for 5 min. Dissolve gelatin by placing the bowl over a small pot of simmering water (I use a jar lid to elevate the bowl above the water). Stir gelatin until fully liquid; set aside to cool.
And now, the cream: Whip cream until it starts to form soft peaks. Add cooled, melted gelatin and continue whipping until cream reaches desired consistency for piped or swirled garnishes. Use as recipe directs.
