How much caster sugar is used for the Vanilla Shortbread? It doesn't say in the recipe.
Nigella's Vanilla Shortbread (from NIGELLA SUMMER) is made by mixing the dough in a food processor and then pressing it into a swiss roll tin (jelly roll pan) before baking. After baking the cooled shortbread is cut into slices and sprinkled with caster (superfine) sugar.
The amount of caster sugar is not specified as it will vary slightly, depending on the dimensions of the tin. You should aim for a thin, even coating of sugar on each slice. It can help to hold a teaspoon of caster sugar above the shortbread slice and tap the spoon gently with a finger, so that the sugar showers down to give an even coating.