Place macaroons on a baking sheet. Bake at 300° for 15 minutes or until lightly browned. Cool completely. Place macaroon pieces between two pieces of waxed paper; using a rolling pin, finely crush macaroons. Combine macaroon crumbs and butter in a small mixing bowl, stirring to blend well. Set aside 1/4 cup crumb mixture. Place remaining mixture in a plastic wrap-lined 6 1/2-cup ring mold. Press crumbs on bottom and halfway up sides of mold. Set mold aside.
Soften gelatin in cold water; set aside. Place 1 cup rum in top of a double boiler. Heat over boiling water. Remove from heat. Add softened gelatin, stirring until gelatin dissolves. Cool completely.
Beat egg yolks in a medium mixing bowl until thick and lemon colored. Gradually add 1/2 cup sugar, beating constantly. Add cooled rum - gelatin mixture; beat well.
Beat 1 cup whipping cream until foamy. Gradually add 1/2 cup sugar, 1 tablespoon at a time, beating until soft peaks form. Fold into rum mixture.
Beat egg whites (at room temperature) until foamy. Gradually add remaining 1/2 cup sugar, 1 tablespoon at a time, beating until stiff peaks form. Fold into rum mixture. Spoon mixture into prepared mold. Cover and refrigerate overnight.
Beat remaining 1 cup whipping cream until foamy. Gradually add 2 tablespoons sugar and 1 tablespoon rum, beating until soft peaks form. Unmold mousse onto a serving platter. Garnish with whipped cream and reserved crumb mixture. Slice and serve immediately.