Turn the oven down to 175°c/155°c fan (347°f/311°f).
Place the golden syrup, brown sugar, salt & cinnamon into a large mixing bowl then set to one side.
Next, brown the butter. To do this, chop the butter into evenly sized pieces then place into a medium saucepan. Place over a medium heat & allow to melt, stirring regularly with a spatula. Keep cooking, until the butter starts to foam, smells nutty & you can see that the milk solids in the bottom of the pan have turned golden brown.
As soon as the brown butter is ready, tip it into the bowl with the sugar & golden syrup in then whisk by hand, to combine. Let the mix cool for a couple of minutes.
In the meantime, roughly chop up the toasted pecans then place into the par baked pie crust. Don't make the pecans too small, we want them to be quite chunky!
Next, whisk the eggs into the butter & sugar mix, one at a time then whisk in the vanilla, lemon zest & juice & the bourbon.
Pour the filling over the toasted pecans in the pie crust then arrange the untoasted pecan halves on top in your desired pattern. Bake the pie in the preheated oven for 55 minutes - 1 hour, until the filling is set with a very slight wobble.If the pecans start to brown too much, loosely cover the pie with foil. Once cooked, let the pie cool then chill in the fridge overnight. To serve, cut into portions then allow to warm up to room temperature.