Heat oven to 325 degrees F.
In a medium-size bowl, stir together graham cracker crumbs, butter and sugar until moistened. Press into the bottom and up side of 9-inch tart pan with removable bottom. Bake at 325 degrees for 15 minutes, until lightly browned. Remove from oven and cool completely.
In small saucepan, stir together 1/3 cup of the sugar, 1/2 cup water, egg yolks, gelatin and salt. Heat over medium-low heat, stirring, until slightly thickened and temperature registers 160 degrees on an instant-read thermometer, about 5 minutes. Strain into a large glass or plastic bowl and stir in Baileys.
Beat egg white mixture until soft peaks form. Gradually beat in remaining 1/3 cup sugar until the peaks are stiff. In medium-size bowl, beat the heavy cream to form soft peaks, and refrigerate.
Place bowl of egg yolk mixture in large bowl of ice water. Stir occasionally until mixture mounds slightly, 8 to 10 minutes.
Fold beaten whites into yolk mixture. Fold in whipped cream until no streaks of white remain. Spoon into crust; cover. Refrigerate for at least 2 hours. Garnish with cocoa power and chocolate- covered coffee beans, if desired. Makes 8 servings.