Blackberry Topping: Puree the blackberries and strain them to remove seeds. Combine the puree with sugar and cornstarch in a small saucepan. Cook over medium heat, stirring constantly, until the mixture thickens. Set aside to cool.

Crust: Preheat the oven to 325°F (162°C). Mix the graham cracker crumbs, sugar, and melted butter in a bowl. Press the mixture firmly into the bottom of cupcake liners in a muffin pan. Bake for 5 minutes, then set aside.

Cheesecake Filling: In a large bowl, beat the cream cheese, sugar, and flour until smooth. Add the sour cream, lavender extract, and vanilla extract, and mix well. Add the eggs one at a time, mixing just until combined. If desired, add a small amount of violet gel icing color to tint the batter. Pour the filling over the crusts, filling each liner almost to the top.

Bake: Reduce the oven temperature to 300°F (148°C). Bake the cheesecakes for 18-20 minutes, or until the centers are set. Turn off the oven and leave the door closed for 10 minutes. Then, crack the oven door slightly and let the cheesecakes cool in the oven for an additional 15-20 minutes. Remove from the oven and refrigerate until fully chilled.

Assemble: Once the cheesecakes are chilled, top each one with a spoonful of blackberry topping. Whip the heavy cream, powdered sugar, and vanilla extract until stiff peaks form. If desired, add violet gel icing color to the whipped cream. Pipe the whipped cream on top of the blackberry topping and garnish each cheesecake with a fresh blackberry.