I stabilize whipped cream by using a TBS of instant pudding powder to one cup of cream. I like the white chocolate flavour as it doesn't add any flavour to the whipped cream. Vanilla can be used as well but it adds a bit of "pudding" flavour. What I do is whip the cream until its doubled in bulk but not firm. Sprinkle on the pudding powder while continuing to whip. It firms up really fast and will stay firm. It does add a bit of sweetness, but not enough to be off-putting.