Preheat oven to 350°.
To prepare crust, combine cracker crumbs and 2 tablespoons sugar, stirring well with a whisk. Add butter and 1 egg white; toss with a fork until moist. Press mixture into bottom and up sides of a 9-inch pie plate coated with cooking spray. Bake at 350° for 8 minutes; cool completely on a wire rack.
To prepare filling, brew water and coffee in a coffee maker according to manufacturer's directions. Place brewed coffee in a small saucepan; bring to a boil. Cook until reduced to 1/3 cup (about 15 minutes). Add marshmallows and milk. Cook over medium heat until marshmallows melt, stirring constantly. Pour mixture into a large bowl; cover and let stand until mixture thickens, stirring occasionally (about 30 minutes).
Place 2 egg whites in a medium bowl; beat with a mixer at high speed until foamy. Gradually add 2 tablespoons sugar, beating at high speed until stiff peaks form. Gently fold half of egg white mixture into marshmallow mixture; gently fold in remaining egg white mixture. Fold in 1 2/3 cups whipped topping. Spoon filling into prepared crust. Cover with plastic wrap; chill until firm (about 5 hours to overnight).
Cut pie into 8 wedges. Top each serving with 1 tablespoon whipped topping (reserve remaining whipped topping for another use); sprinkle each serving with about 1 teaspoon grated semisweet chocolate.