Preheat the oven to 350 degrees Fahrenheit and place rack in center of oven.
Take half of the dough and turn out onto a floured work surface. Using a rolling pin, roll out to a thickness of roughly 1/4".
Place dough in pie tin and set aside.
In a large bowl, combine the golden syrup, brown sugar, eggs, melted butter, salt, vanilla extract, and bourbon and whisk to combine. If using golden syrup, heat the golden syrup up so that its easy to mix with the other ingredients.
Roughly chop the bittersweet chocolate and add the mixture along with the pecans and mix until combined.
Pour mixture into prepared pie crust.
Bake pie for 30 minutes. Remove pie from oven and cover pie crust with tin foil. Place pie back in the oven and bake for another 20 minutes with the foil on the crust.
Remove pie from oven and let cool. Pie can be stored in the fridge overnight if necessary and reheated the next day.