Traditional Pennsylvania Dutch Shoofly Pie vs Traditional Golden Treacle Tart

Both desserts are built on a pourable sweet filling, but they put butter and egg to work in different places. In the shoofly pie, cold butter is rubbed with flour and brown sugar into crumbs, which are layered with a liquid of molasses, hot water, egg and dissolved baking soda, then baked until set yet slightly soft in the centre. The treacle tart keeps its butter and sugar in the shortcrust pastry, while egg binds warmed golden syrup, lemon zest and juice, and fresh breadcrumbs. Under its lattice, that filling bakes to a lightly caramelised sheen with a gentle wobble, the lemon brightening the syrup.