Scald 3 1/2 cups milk in top of a double boiler; gradually stir in 1 1/4 cups sugar. Beat egg yolks until thick and lemon colored. Stir a small amount of hot milk mixture into egg yolks; add to remaining hot milk mixture. Cook, stirring constantly with a metal spoon, until mixture thickens and coats the spoon. Remove from heat.
Soften gelatin in remaining milk; add softened gelatin and crushed macaroons to hot milk mixture; stir well. Chill until consistency of unbeaten egg whites.
Beat egg whites (at room temperature) until soft peaks form. Gradually add remaining 1/4 cup sugar, beating until stiff peaks form. Fold egg whites into gelatin mixture, and spoon into a lightly oiled 8-cup mold. Chill overnight.
Unmold pudding onto a serving platter, and garnish with sliced almonds. Spoon into individual serving bowls.