Chantilly cream is simply whipped cream with vanilla and sugar added. It's really easy to make, and totally addictive.
If you're using a vanilla pod or bean, slit it open lengthways and scrape out the seeds. Add them to the cream in a large bowl. Whisk the cream until you have almost achieved stiff peaks, then add as much sugar as you like. Continue whisking until all the sugar is incorporated.
The cream will keep in the fridge for a few hours, after that it will lose its stiffness, but will still be fine to eat.