Royal Icing

2 egg whites, large

2 tsp. vanilla

1/2 tsp. brown food coloring

3 c. powdered sugar

Beat egg whites, vanilla and food coloring until frothy. Add powdered sugar and continue beating on low until smooth. For a thinner consistency, add water about 1/2 tsp. at a time. If you make it too thin, just mix in a little more powdered sugar. 

Source: Adapted from Joy of Cooking