To make the toffee crunch, in heavy 2-quart saucepan, combine the sugar, butter and vanilla and bring to a boil,  stirring constantly. Reduce the heat to medium and cook, stirring constantly, until the mixture reaches 300°F on a candy thermometer.

Immediately pour the toffee onto an ungreased large cookie sheet. If necessary, quickly spread the mixture to 1/8-inch thickness.

Let the toffee stand at room temperature for about 1 hour, or refrigerate until firm. Break into bite-size pieces, then smash with a rolling pin until crumbly.

To prepare the pastry, spray the base and sides of 2-inch round tart tins with nonstick cooking spray.

In a food processor, combine the flour, cocoa, sugar, salt and butter and process until the mixture resembles fine bread crumbs. Slowly add 2 to 3 tablespoons ice water and pulse until the mixture forms a ball. Remove the dough from the processor, wrap in plastic wrap and refrigerate for 20 minutes.

Preheat the oven to 350°F. 

Roll out the pastry 1/4 inch thick and cut out rounds with a 3-inch round cutter. Line the tart tins with the pastry rounds. Put the pastry-lined tins in the freezer for 15 minutes.

Top each tart with parchment paper and dried beans to weigh it down. Bake for 12 minutes, then remove the parchment and beans and bake for 10 to 12 minutes. Let the pastry shells cool, then remove from the tins. 

To prepare the filling, in a saucepan over medium heat, bring the cream to a simmer. Add the chocolate, remove from the heat and let stand for 3 minutes, then whisk until smooth. Add the Chambord and whisk to combine. Let cool to room temperature. 

Pour the filling into the pastry shells and let the tarts set at room temperature for 4 to 6 hours. 

Top the tarts with fresh blackberries and toffee crunch and serve.