For the Shortcrust Pastry:Place the flour and salt in a food processor and pulse to blend. Next add the cold butter and lard. Pulse a few more times until the mixture resembles coarse crumbs. Add the water a little at a time, pulsing between additions, until the mixture begins to come together. DO NOT over-mix the dough or the pastry crust will be tough and won't be flaky.The mixture is done when it resembles large streusel-like crumbs and when you take some and press it between your fingers it will hold together.Form the dough into a ball, flatten into a 1-inch thick disk, wrap in plastic wrap and refrigerate for at least 30 minutes before using. (The shortcrust pastry can be refrigerated for a few days or frozen for up to 3 months.)
Preheat the oven to 375 degrees F.Roll out the pastry dough. I find it easiest to roll it out on to plastic wrap, it makes transferring it to the tart pan easy. Roll the pastry dough out so that there's a little excess around all sides of the tart pan (it will shrink when baked). You will need a 9-inch fluted tart pan with a removable bottom (also commonly called quiche pans).Carefully place the pastry crust into the tart pan and pierce it multiple times with a fork.Line the pastry crust with parchment paper and fill it with dried beans or similar.Place the tart on the middle shelf of the oven and bake for 10-15 minutes.Remove the beans and parchment paper and continue to bake for another 5-10 minutes or until the crust is a very pale golden.
For the treacle filling: While the shortcrust is baking prepare the filling.Place the golden syrup, lemon zest and lemon juice in a medium saucepan. Heat the syrup until hot and runny and then stir in the breadcrumbs. Turn off the heat and let the mixture sit for 5 minutes.Lightly beat the egg and cream together with a fork. Pour the egg/cream mixture into the saucepan with the treacle mixture and stir quickly to combine.Pour the hot mixture into the tart crust.Place the tart on the middle shelf of the oven (still heated at 375 degreesF) and bake for 20-25 minutes or until the pastry is golden and the filling is nicely browned.Remove the tart from the oven and let it cool.
Treacle tart is traditionally served warm with clotted cream, whipped cream, ice cream, or custard.