For the shortcrust pastry, place flour, carob powder, sugar, xanthan gum and salt together in a food processor, pulsing until combined. Add diced butter, pulsing until mixture resembles fine breadcrumbs.
In a small bowl combine carob syrup and yolk, stirring until combined. Add to the flour mixture, pulsing until combined. Add 1 tablespoon water and pulse until dough just comes together. Add extra water, if required to form a dough. Roll pastry between two sheets of baking paper and line a 22cm (9") fluted loose bottom tart tin with pastry and prick the base. Place tart tin on a baking tray in refrigerator for 30 minutes.
Preheat oven to 190°C (170°C fan forced/325°F).
Place tart tin on a baking tray in preheated oven for 20 minutes to blind bake. Remove from oven and allow to cool. Reduce oven temperature to 160°C (140°C fan-forced/300°F).
For the pie filling, finely chop half the pecan nuts for the filling, setting aside until required. Set the remaining whole nuts aside to decorate the pie top.
In a large mixing bowl combine eggs, sugar, carob syrup, melted butter, brandy, carob powder, flour, spices, zest and vanilla, stirring until well-combined. Add chopped pecan nuts, stirring until combined. Carefully pour mixture into blind baked tart shell and decorate the top with reserved whole pecan nuts.
Place tart tin on baking tray in preheated oven for 45 minutes or until golden and set.
Remove from oven and allow to cool.
Serve carob pecan pie with whipped cream (or vanilla ice cream).