From the zest and juice of citrus fruits, the glaze can then be made in an amount that will ice about 30 cookies by combining:
Thin Glaze
1/2 c. powdered sugar
1 T. juice
1 t. extract
~1/4 – 1/2 t. of the zest
Combine the powdered sugar and juice in a small bowl and stir until well mixed. Stir in the extract. Stir in the zest. The icing should be of a consistency that will spread slightly when applied to the cookies so that it forms a thin, smooth glaze. If the icing is too thick, add juice in small amounts to correct.
Thick Glaze
3/8 c. powdered sugar
1/2 – 1 T. juice
1/4 t. citrus oil
Place the powdered sugar in a small bowl and work in the juice in small amounts until there is just enough to dissolve all the sugar. Add the citrus oil and stir. Food coloring may be added at this stage, but do this very carefully as adding just one drop directly from the bottle may produce a color that is too intense (try using a toothpick instead).
Notes:
A. When you remove the zest from the fruit, you want to just skin the surface, without taking the white pith. Using a microplane with a light touch works well for this.
B. It may seem like you are adding a lot of extract or oil, but you will need this to allow the citrus flavor to emerge over the sweetness of the sugar.
C. This citrus-flavored glaze works well on sugar cookies or gingerbread cookies.
D. This glaze sets up quickly, so if you want to use sprinkles for additional decoration, shake onto each cookie right after spreading on the glaze.