Make the blackberry topping: Puree and strain the blackberries to remove seeds. In a saucepan, combine the puree, sugar, and cornstarch. Cook over medium heat, stirring constantly until thickened. Set aside to cool completely.

Prepare the crust: Preheat the oven to 325°F (162°C). Mix graham cracker crumbs, sugar, and melted butter until combined. Line a cupcake pan with paper liners and press the mixture firmly into the bottoms. Bake for 5 minutes, then let cool.

Make the cheesecake filling: In a large bowl, beat cream cheese, sugar, and flour until smooth. Add sour cream, lavender extract, and vanilla, mixing well. Add eggs one at a time, mixing after each addition. (Optional: Stir in a drop or two of violet gel color for a pastel hue.)

Bake the cheesecakes: Reduce oven temperature to 300°F (148°C). Fill each crust with cheesecake batter. Bake for 18–20 minutes, until centers are just set. Turn off the oven, keep the door closed for 10 minutes. Then crack the door and cool for another 15–20 minutes. Remove and cool completely at room temperature. Refrigerate for at least 2 hours before topping.

Finish and serve: Spoon blackberry topping over each mini cheesecake. In a separate bowl, whip the heavy cream, powdered sugar, and vanilla until stiff peaks form. (Optional: add a touch of gel icing color.) Pipe or dollop whipped cream on top and garnish with a fresh blackberry.