In blender or processor combine: blackberries, ¼ cup of granulated sweetener, and lemon juice. Pulse until puréed. Set aside.
In a stand mixer or large bowl with an electric hand mixer, add heavy whipping cream. Beat on high until firm peaks form, and when you lift the beater, the cream sticks and does not fall off (can take 4 to 6 minutes).
Add vanilla and turn the mixer to medium, and slowly add remaining granulated sweetener a little at a time until blended and the whipped cream is thicker like a frosting. Turn off mixer.
Add ⅔ of the blackberry puree to the whipped cream mixture and very gently fold in (do not mix in or stir in fully, as it should be streaky in the cream).
In a 2.5 to 3.5-ounce dessert cup or 2.5 to 3.5-ounce shot glass, add 1 tablespoon of the remaining blackberry puree to the bottom of each cup.
Add the whipped blackberry cream to the dessert cup and fill it to the top. Use any remaining blackberry puree to drizzle over the top.
Serve immediately, or cover and refrigerate to serve later. Store covered in the fridge for up to 3 days.
*all nutritional data are estimates based on the products I used*Yield: 4 servings, Serving size: one @ 3 ounce fool, Net Carbs per Serving: 2g, Amounts per serving-