Tart Crumb Base Not Setting

Our answer

Nigella's Bitter Orange Tart (from SIMPLY NIGELLA) has a crumb base made from crushed ginger nut biscuits (ginger snap cookies). The crumbs are bound together with softened or melted butter, that firms up when it is refrigerated. It is similar to a cheesecake base or the base used in Nigella's No-Fuss Fruit Tart. Cookies can vary and if the crumb mixture is slightly dry then a little extra butter will usually help to bind it properly. We would mention that the butter should be from a block, as if it is a "spreadable" type of butter from a container then this has added vegetable oil that will keep the butter soft when chilled and will mean that the tart base will not set as well.

It is also important that the biscuits are crushed into small crumbs so that they bind together evenly and pressed firmly into the tart tin. Some people find it helpful to use a potato masher to press the base into place and then a straight-sided glass to press the crumbs into the sides of the tin, or just press very firmly with your fingers or a knuckle.