Grease and line a baking sheet with nonstick baking paper. Put the flour and butter in a food processor and blend until the mixture resembles breadcrumbs. Add the sugar, ground ginger, egg yolks and vanilla bean paste and blend to make a smooth dough. Wrap in clingfilm and chill for at least 1 hour.
Roll out the dough on a lightly floured surface to between 2.5 mm (⅛ inch) and 5 mm (¼ inch) thick and transfer to the baking sheet. Cut off the rough edges, but leave them in position to keep the dough in place. Cut out 12 x 5 cm (2 inches) squares from the dough. Bake in a preheated oven, 180°C (350°F), Gas Mark 4, for 16–18 minutes or until risen slightly and beginning to darken around the edges. Recut the marked lines and transfer the cookies to a wire rack to cool. Beat the icing sugar in a bowl with enough of the lemon or lime juice to give a consistency that thickly covers the back of the spoon. Using a teaspoon, drizzle wavy lines of citrus glaze over the top of a cookie, then brush more around the sides.
Scatter with sugar sprinkles, tipping off the excess, then dip the sides in sugar sprinkles. Transfer the cookie to the baking paper. Repeat with the remaining cookies, then leave in a cool place to set for 2 hours. Stack the cookies in little bundles and tie with ribbon.