Place the blackberries in a medium bowl and sprinkle with the granulated sugar; drizzle with the vanilla; toss lightly to evenly coat.
Allow to steep for 10 minutes; mash the blackberries until they release their juices and form a thick pulp.
In another medium bowl, combine the heavy cream and confectioners’ sugar.
Use an electric stand, hand mixer or whisk to whip the cream to medium peaks: when you lift the beater or whisk, the cream should hold a peak for a moment.
Pour the berry mixture over the cream and use a rubber spatula to gently fold until combined.
You can leave streaks of the berry mixture or completely incorporate it.
Serve immediately or cover and refrigerate for up to 1 day.
To serve, scoop into glasses or dishes and top with whole blackberries.
Serve with shortbread cookies, if desired.
