1. Combine sugar and corn syrup in a saucepan over medium heat. Bring to a boil; reduce heat to low, and simmer 2 minutes, stirring occasionally. Cool completely, about 45 minutes. Let thicken.

2. In the top of a double boiler, combine 2 ounces chocolate and butter over medium-low heat; cook until melted. Set aside to cool.

3. Heat oven to 400 degrees. On lightly floured surface, roll out chocolate-crust dough to a 13-inch circle, 1/8 inch thick. Place dough in pan, and crimp edges. Chill 15 minutes.

4. In a large bowl, beat eggs until foamy. Add chocolate and corn-syrup mixtures to eggs, and combine. Stir in vanilla and pecan halves.

5. Pour filling into crust. Bake 20 minutes. Lower oven to 350 degrees and bake until filling has set, about 20 minutes. Sprinkle with remaining 2 ounces chocolate; bake 5 minutes more. Cool on a wire rack, 1 1/4 hours. Garnish with lavender, if using, and serve with whipped cream or creme fraiche.