Sticky crumble topped gingerbread

Searching for a gingerbread recipe can be a bit confusing – for a start gingerbread can be a rich loaf cake, a pain d’epices, or it can be a crisp biscuit for gingerbread houses or little iced biscuits (see my own recipe for Gingerbread foxes). This is neither! Inspired in part by Grassmere gingerbread (a