Whipped cream, unless a recipe specifically calls for Cool Whip (which has stabilizers, and I'm guessing is why it works in recipes but whipped cream might not). Growing up, we had Dream Whip, which came as a dry packaged product that you mixed into milk and whipped. It was pretty good, better than Cool Whip, IMO.
SO... whipped cream people- freshly whipped, plain or unsweetened, or "squirty cream" from the aerosol can??