Peel and slice aboout 1 to 1 1/2 lbs. (enough to make 1 cup) of the peaches. Place sliced peaches in food processor, food mill or blender to puree peaches. Refrigerate puree.
In top of a double boiler, beat egg yolks with 1/2 c of sugar until thick and lemony in color. Stir in the lemon juice and the peach liqueur. Cook over hot water, stirring constantly, until mixture has thickened, about 4 minutes. Cool to room temp. and fold in peach puree. Chill in refrigerator.
In mixing bowl, beat egg whites until foamy. Gradually add remaining 1/4 c sugar, beating until meringue is stiff. Fold into peach mixture. Spoon peach mousse into 8 custard cups and freeze.
Before serving, peel and slice remaining peaches. To serve, unmold frozen mousse onto individual dessert plates and garnish with sliced peaches. Mousse tastes best if allowed to stand and soften 5 to 10 minutes before serving.
Source: Stanford Court Hotel Judy Garnett