I developed this recipe almost 20 years ago for a Memorial Day party, I was looking for something different to do with rhubarb and hit on this idea. I've made it almost every spring since then. Rhubarb imparts a wonderful tanginess to this ethereal French concoction of air and sweetened cream. For that particular event - and a few times since - I made cupped tuiles out of almond flour to serve the mousse in. The almond presents a nice flavor backdrop to the rhubarb. But the tuiles are just gilding the lily. —Kevin
Peel lime, being careful not to include pith, cut into strips, wrap in plastic, and refrigerate. Squeeze juice from lime(s). You need about 1 tablespoon.
Place rhubarb in a large sauce pan with 2 tablespoons amaretto, water, and 1/4 cup sugar over medium heat. Cook, stirring often, until rhubarb breaks down - about 15 minutes. Transfer to a blender, add gelatin and lime juice, and process until smooth. Taste. The mixture should be fairly tart but should make you pucker. You made need to add a bit more lime juice or a bit more sugar.
In a double boiler, beat the egg yolks with 1/2 cup sugar until they are a pale yellow. Cook over just bubbling water, stirring constantly, until yolks have thickened. Cool to room temperature.
Combine rhubarb mixture with egg mixture. In a large bowl, whip cream until stiff then whip in remaining 2 tablespoons of Amaretto. Fold cream into rhubarb mixture. If you want to serve the mousse in tuiles then chill in a large bowl for at least 3 hours. Otherwise, spoon into individual dessert cups or wine goblets and chill for at least 3 hours. When ready to serve, garnish with strips of lime peel.