2) Bring just to a boil, then reduce heat and simmer, stirring frequently, until reduced to approximately 1 cup.
3) Add liquer, and stir for a few more minutes. Remove from heat, pour into a large mixing bowl and let cool.
4) Whip cream to stiff peaks. Fold cream gently into peach mixture.
5) Spoon into individual dishes, and chill for several hours.
The mousse will freeze surprisingly well, if carefully sealed. A better solution by far is to freeze the peach reduction after step 3. Take advantage of fruit in season, like strawberries or raspberries, and put some up in this form. With a little ingenuity, this fruit reduction might also be used as a pastry filling.