1¼ cups plain flour
¼ cup icing sugar
zest of 1 lemon
100 grams cold butter, diced
1 egg yolk
¼ teaspoon vanilla extract
1-2 tablespoons chilled water
1/3 cup lightly packed brown sugar
1 teaspoon vanilla extract
¼ cup golden syrup
200 grams butter
200 grams walnuts, or mixed nuts
Pastry: Put the flour, icing sugar, salt and lemon zest in the bowl of a food processor and pulse several times to combine. Add the chilled butter and pulse again until the mixture is the texture of fine breadcrumbs. Add the egg yolk, vanilla and 1 tablespoon of the water and continue to process until the mixture just starts to come together. Only add the extra water if necessary. Tip out onto the bench and bring the pastry together with your hands. Form into a flat disc, wrap and refrigerate for 30 minutes.
Preheat the oven to 180°C and put an oven tray in to heat.
Remove the pastry from the fridge and roll out on a lightly floured surface until large enough to fit a 22 cm x 22 cm square, loose-bottomed tart tin. Prick the base several times with a fork. Line the pastry case with baking paper and baking beans and blind bake, on the preheated baking tray, for 15 minutes. Remove the paper and beans and cook for a further 3 minutes.
Combine the brown sugar, vanilla, golden syrup, and butter in a saucepan and bring to the boil. Boil for 3 minutes then stir in the nuts and set aside to cool.
Pour the nut mixture into the hot pastry case and cook for 18-22 minutes or until the filling is bubbling all over and the pastry nicely golden but not too dark.
Cool slightly and serve warm or cold, cut into squares with vanilla ice cream if desired.