I am having trouble with a 'soggy bottom' when I bake shortbread, although I have baked them at the right temperature for the right amount of time - even too long sometimes but they always end up slightly soft underneath. Do you have any idea why this is, and any suggestions to stop this?
Shortbread should always have a tender, melting texture, but be slightly crisp when you bite into it. It should not generally be damp or wet underneath. A classic shortbread recipe will also only have flour, butter and sugar as the ingredients (in a 3:2:1 ratio) and not egg, which could lead to excess moisture.
There are a variety of reasons why the shortbread could be damp underneath but it is most likely that either the dough is being pressed out too thickly, the pan is not metal so heats up too slowly, or the oven temperature is too high causing the top to brown before the bottom has cooked sufficiently. We would recommend trying Nigella's Vanilla Shortbread recipe (from Forever Summer) as this is made in a Swiss roll (jelly roll) pan. The pan is made of metal but also has low sides so should have fairly good heat distribution while the shortbread bakes. Also the recipe bakes the shortbread at 160c/375F which is lower than for normal cookies and helps to cook the cookies thoroughly. It also uses icing sugar (confectioner's sugar) and cornflour (cornstarch) to help give melt-in-the-mouth shortbread.