Dilute almost ⅝ lb sugar with 5–6 glasses water, add the gelatin and the finely peeled zest from 1 lemon, and boil until the gelatin dissolves and the liquid is reduced to 3 glasses. Squeeze the juice from 1 large lemon through a strainer into the jelly. While still warm, begin to beat the mousse with a whisk over ice until it thickens and whitens. One wineglass rum may be added, then pile into a mold and set on ice.
This mousse may be colored with cranberries, squeezing the juice through a cloth so that it is a very light apricot color. Or divide the mousse into 2 parts and color one part red, leaving the other white.