Add the cold heavy whipping cream and vanilla bean paste to a large chilled mixing bowl. Beat on low-medium speed until slightly thickened, then increase to high speed and whip until stiff peaks form. Set aside.

In a separate large bowl, add the softened cream cheese and powdered sugar substitute. Beat on low-medium speed until combined, then increase to high speed and mix until the cream cheese mixture is very light and fluffy, scraping down the bowl as needed.

Gently fold the whipped cream into the cream cheese mixture in 2–3 additions, using a spatula and broad, sweeping motions to keep the mixture airy.

Add the sliced strawberries, blackberries, and raspberries, then gently fold just until the berries are evenly distributed throughout the fluff.

Spoon the Sugar Free Cheesecake Fluff into individual bowls or a serving dish and serve immediately, or chill for 30–60 minutes before serving if you prefer it more set.