(From "Pacific Northwest Palate," by Susan Bradley.)
Sprinkle the brown sugar over the rhubarb and let sit for an hour. Put in a saucepan, cover, and simmer gently for 15 minutes or so, until fully tender and quite thick. Puree in a processor.
Soften the gelatin in the gin for 10 minutes. Combine with the rhubarb and heat to dissolve the gelatin. Set into an ice-water bath (a large bowl filled halfway with ice and a couple of cups of water.) Cool until cold to the touch, but do not allow the gelatin to set.
With an electric mixer, combine the cream and rhubarb mixture. Whip until fluffy and light. Do not overwhip or the cream will break down.
Beat the egg whites until soft peaks form. Add the sugar and continue until stiff peaks have formed. Carefully fold the egg whites into the rhubarb and cream mixture. Turn the mousse into a clear glass, 6-cup, straight-sided souffle dish or into individual 1-cup souffle dishes and refrigerate for 2 hours or more.
To make the Strawberry Gin Sauce, puree the strawberries and sugar together in a processor. Strain through a sieve and reserve. Warm the marmalade just to melt. Combine the marmalade, the gin, and the pureed strawberries, mixing well. Chill thoroughly.
Serve each portion of mousse topped or surrounded with sauce; pass the sauce separately.