Prepare the berries: In a small bowl, mash half of the mixed berries with 1 tablespoon of powdered erythritol. Leave the other half of the berries whole. Set aside.

Whip the cream: In a large mixing bowl, whip the heavy cream, vanilla extract, and remaining 1 tablespoon of powdered erythritol using an electric mixer until soft peaks form.

Fold in the berries: Gently fold the mashed berries into the whipped cream, creating a swirled effect. Be careful not to overmix so the swirl effect stays visible. Fold in the remaining whole berries.

Chill and serve: Divide the mixture into serving glasses or bowls. Refrigerate for about 30 minutes to allow the flavors to meld. Garnish with fresh mint leaves if desired and serve chilled.