Can I Seal The Crust Of The Treacle Slice With Extra Golden Syrup?

Our answer

Nigella's Treacle Slice (from KITCHEN) is a traybake (sheet pan) version of the traditional treacle tart. It has a pastry crust than is blind baked before the filling is added and then cooked again. Blind baking is the best way to prevent a tart from having a soggy bottom as the pastry partly cooks and will absorb less liquid once the filling is added. The blind-baked crust can be sealed and usually this would be done by removing any baking beans and lining paper and then brushing the base of the crust with some beaten egg or lightly beaten egg white and returning it to the oven for 3-5 minutes to let the egg wash set. The egg wash forms a barrier between the crust and the filling, reducing the amount of liquid that seeps from the filling into the crust.

We have not tried sealing a pie or tart crust with syrup, though in theory the sugars will crystallize slightly to form a barrier. But we think that an egg wash would generally be more effective as the liquid in the filling could just dissolve the crystallized sugars. For the Treacle Slice the filling is syrup anyway, so you could try brushing extra syrup onto the crust and then returning it to the oven for a couple of minutes before adding the filling. But we have found that for this recipe just blind baking the crust is sufficient. Also, golden syrup is more viscous than corn syrup, so it will be harder to brush it evenly onto the crust. For a double crust pie, where the base may not be blind baked, it is best to make sure that the crust is completely cooked, as if you try to add anything to seal the crust before baking it will simply get mixed in with the filling ingredients. Using an ovenproof glass pie dish helps as you can see when the crust is golden brown and without any damp, undercooked patches.