Score 1 fresh pomegranate and place in a bowl of water. Break open the pomegranate under water to free the arils (seed sacs). The arils will sink to the bottom of the bowl and the membrane will float to the top.
Sieve and put the arils in a separate bowl. Reserve 1/4 cup of the arils from fruit and set aside. (Refrigerate or freeze remaining arils for another use.)
In a medium sized bowl, beat heavy cream with a wire whisk or electric mixer until slightly thickened.
Add powdered sugar and vanilla, and whip until mixture doubles in volume and soft peaks form. Gently fold in the arils.